ISO 7206-13:2016

Implants for surgery - Partial and total hip joint prostheses - Part 13: Determination of resistance to torque of head fixation of stemmed femoral components

ISO 7206-13:2016 describes a method of determining the torque required, under specified laboratory conditions, to loosen the fixation of the head of hip joint prostheses in which the head is not intended to rotate relative to the neck. It applies to the femoral component of total or partial hip joint replacements in which the head and neck/stem (in the following referred to as cone) are secured together by a locking conical taper or any other means and in which the head and cone are separate components, and which are made of metallic or non-metallic materials. It does not cover methods of examining the test specimens; these should be agreed between the test laboratory and the party submitting the specimen for test.

Implants chirurgicaux — Prothèses partielles et totales de l'articulation de la hanche — Partie 13: Détermination de la résistance au couple de la fixation des têtes des tiges fémorales

General Information

• Status: Published
• Publication Date: 26-Jun-2016
• 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/WG 1 - Mechanical testing
• Current Stage: 9093 - International Standard confirmed
• Start Date: 03-Sep-2021
• Completion Date: 13-Dec-2025

Relations

• Amended By: ISO 7206-13:2016/Amd 1:2022 - Implants for surgery - Partial and total hip joint prostheses - Part 13: Determination of resistance to torque of head fixation of stemmed femoral components - Amendment 1
• Effective Date: 18-Dec-2021

Overview

ISO 7206-13:2016 defines a laboratory method to determine the torque required to loosen the head fixation of stemmed femoral components used in partial and total hip joint prostheses. It applies when the femoral head and neck/stem (the cone) are separate components joined by a locking conical taper or other mechanical means, and covers metallic and non‑metallic materials. The standard focuses on static torque testing under specified conditions; it does not prescribe specimen handling or clinical inspection procedures.

Key topics and technical requirements

• Test principle: Apply a steadily increasing static torque to the head/cone assembly until breakaway (rotation) occurs or a defined maximum is reached.
• Sample size: A minimum of five test specimens per cone unit.
• Assembly and fixation: Assembly follows ISO 7206-10 procedures. Head fixation for torque application can be achieved by:
  • Flattening the head equator to two parallel planes (perpendicular distance 30–70% of head diameter; remaining wall ≥ 2.0 mm). Example: for a 28 mm head, 19.0 mm ± 0.5 mm is suitable.
  • Gluing the head into a metal calotte covering at least 140° of the hemisphere (bond breakaway torque must exceed expected head/cone torque).
  • Embedding the head in cast resin (embedding/bond strength must exceed expected torque).
• Loading rates and limits:
  • Torque loading rate: 20 Ncm/s ± 4 Ncm/s, or rotation rate 0.05°/s ± 0.01°/s.
  • Termination criteria: load peak and decrease, torque limit 50 Nm, or angle limit 20°.
• Apparatus requirements: Testing machine compliant with ISO 7500-1, able to apply axial compressive force for assembly and torque with 1% accuracy; angular displacement measurement to ±0.5°.
• Alignment: Axis alignment and degrees of freedom are required to avoid biased results (fixture ideally allows 5 DOF).
• Performance criteria and reporting:
  • Acceptance criteria are defined by the customer (often relative to clinically successful assemblies) and should include mean and per-sample lower limits.
  • Test report must reference ISO 7206-13 and include specimen identities, fixation method, loading rates, maximum torque/angle at rotation, termination reasons, and observable damage.

Applications and who uses it

• Implant manufacturers - design verification, quality control of modular taper connections and femoral head fixation strength.
• Test laboratories - standardized procedures for reporting breakdown torque and generating comparative data.
• Regulatory bodies and notified bodies - evidence of mechanical stability for conformity assessment and pre‑market submissions.
• R&D and failure analysis teams - development of taper geometries, material pairings, and assembly processes to reduce fretting and micromotion.

Related standards

• ISO 7206 series (e.g., ISO 7206-1, ISO 7206-10) - dimensions and static load procedures for femoral heads.
• ISO 7500-1 - verification and calibration requirements for testing machines used in this test.

Keywords: ISO 7206-13:2016, hip joint prostheses, torque resistance, head fixation, stemmed femoral components, taper connection, implant testing, femoral head torque test.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 7206-13
First edition
2016-07-01
Implants for surgery — Partial and
total hip joint prostheses —
Part 13:
Determination of resistance to torque
of head fixation of stemmed femoral
components
Implants chirurgicaux — Prothèses partielles et totales de
l’articulation de la hanche —
Partie 13: Détermination de la résistance au couple de la fixation des
têtes des tiges fémorales
Reference number
©
ISO 2016
© ISO 2016, 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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ii © ISO 2016 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
6 Procedure. 2
6.1 Test specimen and sample size . 2
6.2 Assembly of test specimen (installation) . 2
6.3 Head fixation . 2
6.4 Torque of head fixation . 3
6.5 Performance criteria . 3
6.6 Test report . 3
7 Disposal of test specimens . 4
Bibliography . 6
Foreword
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electrotechnical standardization.
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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
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on the ISO list of patent declarations received (see www.iso.org/patents).
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For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 150, Implants for surgery, Subcommittee SC 4,
Bone and joint replacements.
ISO 7206 consists of the following parts, under the general title Implants for surgery — Partial and total
hip joint prostheses:
— Part 1: Classification and designation of dimensions
— Part 2: Articulating surfaces made of metallic, ceramic and plastics materials
— Part 4: Determination of endurance properties of stemmed femoral components
— Part 6: Endurance properties testing and performance requirements of neck region of stemmed femoral
components
— Part 10: Determination of resistance to static load of modular femoral heads
— Part 12: Deformation test method for acetabular shells
— Part 13: Determination of resistance to torque of head fixation of stemmed femoral components
iv © ISO 2016 – All rights reserved

Introduction
Some designs of stemmed femoral components of total hip joint prostheses comprise a
stem/neck component and a bearing head component, which is commonly in the form of a partial
sphere incorporating a female fixation feature for attachment to the neck of the stem. Such heads are
generally produced using metal or ceramic material. It is important that after assembly, whether by
the manufacturer or by the surgeon in the operating theatre, the head subsequently remains immobile
on the neck, because movement of a metal or a ceramic femoral head component on a metal stem/neck
component will cause the metal components to wear, while metal-on-metal movement may lead to
severe fretting corrosion (see Reference [1]).
It is essential, therefore, that the strength of the fixation between the head and the neck is sufficient
to withstand the torque likely to be transmitted through the prosthesis in use. The maximum torque
applied to the interface connection depends on several design, material, and manufacturing specific
parameters, e.g. pairing of bearing materials, bearing diameter, and clearance, surface finish, etc. (see
Reference [2]).
The locking strength of the interface connection depends on several design, material, and manufacturing
specific parameters for the taper geometry of the mating components, as taper angle and tolerances, taper
clearance, surface finish, etc. In consequence, the torsional locking strength of nominal identical taper
fixations might vary significantly (see Reference [3]) and needs to be determined prior to clinical use.
Clinical failure of taper connections is related to particle generation by interface micromotion, fretting,
and fatigue failure (see Reference [4]). Torsional interface stability is essential for stable fixation of
taper connections in order to limit the above listed adverse effects.
INTERNATIONAL STANDARD ISO 7206-13:2016(E)
Implants for surgery — Partial and total hip joint
prostheses —
Part 13:
Determination of resistance to torque of head fixation of
stemmed femoral components
1 Scope
This part of ISO 7206 describes a method of determining the torque required, under specified laboratory
conditions, to loosen the fixation of the head of hip joint prostheses in which the head is not intended to
rotate relative to the neck. It applies to the femoral component of total or partial hip joint replacements
in which the head and neck/stem (in the following referred to as cone) are secured together by a locking
conical taper or any other means and in which the head and cone are separate components, and which
are made of metallic or non-metallic materials.
This part of ISO 7206 does not cover methods of examining the test specimens; these should be agreed
between the test laboratory and the party submitting the specimen for test.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only t
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