ISO 21536

Non-active surgical implants — Joint replacement implants — Specific requirements for knee-joint replacement implants

This document specifies requirements for knee-joint replacement implants. Regarding safety, this document specifies requirements for intended performance, design attributes, materials, design evaluation, manufacture, sterilization, packaging, information supplied by the manufacturer and methods of test. This document applies to both total and partial knee joint replacement implants. It applies to these replacements both with and without the replacement of the patella-femoral joint. It applies to components made of metallic and non-metallic materials. This document applies to a wide variety of knee replacement implants, but for some specific knee replacement implant types, some considerations, not specifically covered in this document, can be applicable. Further details are given in 7.2.1.2. The requirements which are specified in this document are not intended to require the re-design or re-testing of implants which have been legally marketed and for which there is a history of sufficient and safe clinical use. For such implants, compliance with this document can be demonstrated by providing evidence of the implant’s sufficient and safe clinical use.

Implants chirurgicaux non actifs — Implants de remplacement d'articulation — Exigences spécifiques relatives aux implants de remplacement de l'articulation du genou

Le présent document spécifie les exigences relatives aux prothèses de l'articulation du genou. En matière de sécurité, le présent document fournit des exigences relatives aux performances prévues, à la conception, aux matériaux, à l'évaluation de la conception, à la fabrication, à la stérilisation, à l'emballage et aux informations devant être fournies par le fabricant ainsi que des méthodes d'essai. Le présent document s'applique à la fois aux implants de remplacement total et partiel de l'articulation du genou. Il s'applique à ces remplacements avec et sans remplacement de l'articulation fémoro-patellaire. Il s'applique aux composants fabriqués en matériaux métalliques et non métalliques. Le présent document s'applique à une grande variété d'implants, mais certaines considérations, non spécifiquement couvertes dans le présent document, peuvent être applicables à certains types spécifiques d'implants de remplacement de l'articulation du genou. Voir 7.2.1.2 pour plus de détails. Les exigences spécifiées dans le présent document n'ont pas pour but d'exiger une nouvelle conception ou de nouveaux essais sur des implants qui ont été légalement mis sur le marché et pour lesquels il existe un historique d'utilisation clinique suffisante et sans danger. Pour ces implants, la conformité au présent document peut être démontrée en fournissant la preuve d'une utilisation clinique suffisante et sans danger de l'implant.

General Information

• Status: Not Published
• 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 4 - General requirements
• Current Stage: 6000 - International Standard under publication
• Completion Date: 04-May-2023

Relations

• Revises: ISO 21536:2007 - Non-active surgical implants — Joint replacement implants — Specific requirements for knee-joint replacement implants
• Effective Date: 10-Jul-2021
• Revises: ISO 21536:2007/Amd 1:2014 - Non-active surgical implants — Joint replacement implants — Specific requirements for knee-joint replacement implants — Amendment 1
• Effective Date: 23-Apr-2020

Standards Content (Sample)

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 21536
ISO/TC 150/SC 4
Non-active surgical implants —
Secretariat: BSI
Joint replacement implants —
Voting begins on:
2023-03-08 Specific requirements for knee-joint
replacement implants
Voting terminates on:
2023-05-03
Implants chirurgicaux non actifs — Implants de remplacement
d'articulation — Exigences spécifiques relatives aux implants de
remplacement de l'articulation du genou
ISO/CEN PARALLEL PROCESSING
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 21536:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 1 ----------------------
ISO/FDIS 21536:2023(E)
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 21536
ISO/TC 150/SC 4
Non-active surgical implants —
Secretariat: BSI
Joint replacement implants —
Voting begins on:
Specific requirements for knee-joint
replacement implants
Voting terminates on:
Implants chirurgicaux non actifs — Implants de remplacement
d'articulation — Exigences spécifiques relatives aux implants de
remplacement de l'articulation du genou
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
ISO/CEN PARALLEL PROCESSING

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.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
ISO copyright office
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
CP 401 • Ch. de Blandonnet 8
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
CH-1214 Vernier, Geneva
DOCUMENTATION.
Phone: [phone]
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: [e-mail]
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 21536:2023(E)
Website: www.iso.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
© ISO 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 2 ----------------------
ISO/FDIS 21536:2023(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .............................................................................................................................................................................................................................. vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 2

4 Intended performance ...................................................................................................................................................................................6

5 Design attributes .................................................................................................................................................................................................6

5.1 General ........................................................................................................................................................................................................... 6

5.2 Tolerances and dimensions ......................................................................................................................................................... 7

5.2.1 Tolerances and dimensions of taper connections ................................................................................. 7

5.2.2 Surface finish of non-articulating regions of knee joint components ................................. 8

5.2.3 Surface finish of articulating surfaces of knee joint components .......................................... 8

5.3 Thickness of knee joint components ................................................................................................................................... 8

5.3.1 General ........................................................................................................................................................................................ 8

5.3.2 Thickness of UHMWPE in tibial inserts, monobloc tibial components,
mobile­bearing components, patella inserts and monobloc patellar

components ............................................................................................................................................................................. 8

5.3.3 Thickness of metal and ceramic in femoral components, tibial trays and

patellar trays ................................... ........................................................................................................ ............................... 9

6 Materials ....................................................................................................................................................................................................................10

7 Design evaluation ............................................................................................................................................................................................10

7.1 General ........................................................................................................................................................................................................ 10

7.2 Pre­clinical evaluation ........................................................................................................................................... ....................... 10

7.2.1 General ..................................................................................................................................................................................... 10

7.2.2 Test methods and performance requirements .....................................................................................12

7.3 Clinical investigation ..................................................................................................................................................................... 18

7.4 Post market surveillance ............................................................................................................................................................ 19

8 Manufacture ..........................................................................................................................................................................................................19

9 Sterilization ............................................................................................................................................................................................................19

10 Packaging..................................................................................................................................................................................................................19

11 Information to be supplied by the manufacturer ..........................................................................................................19

11.1 General ........................................................................................................................................................................................................ 19

11.2 Product type and dimensions ................................................................................................................................................ 19

11.3 Constructional and functional compatibility of components .................................................................... 20

11.4 Marking ...................................................................................................................................................................................................... 20

11.5 Information for the patient ....................................................................................................................................................... 20

11.6 Electronic instructions for use ............................................................................................................................................. 20

Annex A (informative) Evaluation of the range of relative angular motion of components of

fully constrained total knee joint replacement implants .....................................................................................21

Annex ZA (informative) Relationship between this European standard and the General

Safety and Performance Requirements of Regulation (EU) 2017/745 aimed to be

covered ........................................................................................................................................................................................................................22

Bibliography .............................................................................................................................................................................................................................25

iii
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ISO/FDIS 21536:2023(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 of 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

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, in collaboration with the European Committee for Standardization

(CEN) Technical Committee CEN/TC 285, Non-active surgical implants, in accordance with the Agreement

on technical cooperation between ISO and CEN (Vienna Agreement).

This third edition cancels and replaces the second edition (ISO 21536:2007), which has been technically

revised. It also incorporates the Amendment ISO 21536:2007/Amd 1:2014.
The main changes are as follows:

— The scope has been expanded to specify more precisely the knee joint replacement types which are

the subject of this document. Also, the scope now clarifies the requirements for implants which have

been legally marketed and for which there is a history of sufficient and safe clinical use.

— The number of normative references has been expanded, including the addition of several ASTM

standards.

— Several new definitions have been added, including: maximum claimed flexion, mobile-bearing

component, mobile-bearing knee joint prosthesis, partial knee joint prosthesis and partial knee

joint replacement, posterior stabilized tibial insert, reference implant, sufficient and safe clinical

use, tibial insert, total knee joint prosthesis and total knee joint replacement, ultra-high molecular

weight polyethylene and UHMWPE, uni-compartmental knee joint replacement and UKR, and worst

case.

— The design attributes to be taken into account have been specified in Clause 5. The requirements

for the thickness of various knee joint components made from plastic, metal and ceramic have been

expanded.
— Several new general requirements have been added in 7.2.1, which specify
a) the circumstances when a test can be omitted,
b) the testing of the worst case,
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ISO/FDIS 21536:2023(E)

c) the processes to be followed when no performance requirement has been specified, and

d) the processes to be followed when a performance requirement has been specified but has not

been met.

— The number of pre-clinical evaluations (bench tests) to be performed has been greatly increased

in 7.2.2. For some of the tests, a performance requirement has been specified. For some of the

tests no performance requirement has been specified and, in these cases, a new requirement has

been added, namely the requirement to demonstrate that the performance of the implant under

evaluation is the same or better than that of a reference implant. If no reference implant exists, a

sequence of alternative options has been specified. These alternative options are also available in

the case where there is a performance requirement, which is not met by the implant being tested.

— A new clinical investigation subclause has been added in 7.3, with several requirements which

specify the circumstances in which a clinical investigation can be required.

— A new post-market surveillance subclause has been added in 7.4, which references the requirements

in ISO 21534:2007, 7.4.
— Several new marking requirements have been specified in 11.4.

— A note has been added in 11.6 which states that in some jurisdictions there is the option to provide

the instructions for use in electronic instead of paper format.

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.
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ISO/FDIS 21536:2023(E)
Introduction

There are three levels of standards dealing with non­active surgical implants. These are as follows,

with level 1 being the highest:

— level 1: general requirements for non-active surgical implants and instrumentation used in

association with implants;
— level 2: particular requirements for families of non-active surgical implants;
— level 3: specific requirements for types of non-active surgical implant.

This document is a level 3 standard and contains requirements applying specifically to knee joint

replacements.

The level 1 standard, ISO 14630, contains requirements that apply to all non-active surgical implants. It

also indicates that there are additional requirements in the level 2 and level 3 standards.

The level 2 standards apply to more restricted sets or families of implants such as those designed for

use in osteosynthesis, cardiovascular surgery or joint replacement. For joint replacement implants, the

level 2 standard is ISO 21534.

To address all requirements, it is recommended that a standard of the lowest available level be consulted

first.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 21536:2023(E)
Non-active surgical implants — Joint replacement implants
— Specific requirements for knee-joint replacement
implants
1 Scope

This document specifies requirements for knee-joint replacement implants. Regarding safety, this

document specifies requirements for intended performance, design attributes, materials, design

evaluation, manufacture, sterilization, packaging, information supplied by the manufacturer and

methods of test.

This document applies to both total and partial knee joint replacement implants. It applies to these

replacements both with and without the replacement of the patella-femoral joint. It applies to

components made of metallic and non­metallic materials.

This document applies to a wide variety of knee replacement implants, but for some specific knee

replacement implant types, some considerations, not specifically covered in this document, can be

applicable. Further details are given in 7.2.1.2.

The requirements which are specified in this document are not intended to require the re-design or re-

testing of implants which have been legally marketed and for which there is a history of sufficient and

safe clinical use. For such implants, compliance with this document can be demonstrated by providing

evidence of the implant’s sufficient and safe clinical use.
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 5834­1, Implants for surgery — Ultra-high-molecular-weight polyethylene — Part 1: Powder form

ISO 7207­1:2007, Implants for surgery — Components for partial and total knee joint prostheses — Part 1:

Classification, definitions and designation of dimensions

ISO 7207­2, Implants for surgery — Components for partial and total knee joint prostheses — Part 2:

Articulating surfaces made of metal, ceramic and plastics materials

ISO 10993­1, Biological evaluation of medical devices — Part 1: Evaluation and testing within a risk

management process

ISO 14243­1, Implants for surgery — Wear of total knee-joint prostheses — Part 1: Loading and

displacement parameters for wear-testing machines with load control and corresponding environmental

conditions for test

ISO 14243­2, Implants for surgery — Wear of total knee-joint prostheses — Part 2: Methods of measurement

ISO 14243­3, Implants for surgery — Wear of total knee-joint prostheses — Part 3: Loading and

displacement parameters for wear-testing machines with displacement control and corresponding

environmental conditions for test

ISO 14243­5, Implants for surgery — Wear of total knee prostheses — Part 5: Durability performance of

the patellofemoral joint
ISO 14630, Non-active surgical implants — General requirements
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ISO/FDIS 21536:2023(E)

ISO 14879­1, Implants for surgery — Total knee-joint prostheses — Part 1: Determination of endurance

properties of knee tibial trays

ISO 21534:2007, Non-active surgical implants — Joint replacement implants — Particular requirements

ASTM F648, Standard Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated

Form for Surgical Implants

ASTM F1223, Standard Test Method for Determination of Total Knee Replacement Constraint

ASTM F2722, Standard Practice for Evaluating Mobile Bearing Knee Tibial Baseplate Rotational Stops

ASTM F2723, Standard Test Method for Evaluating Mobile Bearing Knee Tibial Baseplate/Bearing

Resistance to Dynamic Disassociation
ASTM F2724, Standard Test Method for Evaluating Mobile Bearing Knee Dislocation

ASTM F2777, Standard Test Method for Evaluating Knee Bearing (Tibial Insert) Endurance and Deformation

Under High Flexion

ASTM F3210, Standard Test Method for Fatigue Testing of Total Knee Femoral Components under Closing

Conditions
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 14630, ISO 21534 and

ISO 7207-1 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
femoral component

component of a total knee joint prosthesis (3.14), patella-femoral knee joint prosthesis, or uni-

compartmental knee joint prosthesis (3.16) intended to be secured to the femur to replace its articulating

surface(s)
3.2
maximum claimed flexion

highest amount of flexion the total knee joint prosthesis (3.14) or uni-compartmental knee joint prosthesis

(3.16) can achieve as claimed by the manufacturer based on the requirements defined in 7.2.2.11

Note 1 to entry: A higher amount of flexion than the maximum claimed flexion can exist based on computer aided

design (CAD) or implant shape considerations.
3.3
mobile-bearing component

component of a total or uni­compartmental mobile-bearing knee joint prosthesis (3.4) which articulates

with both the femoral component (3.1) and the tibial tray (3.13)

Note 1 to entry: The mobile-bearing component can be manufactured as one component or a set of components,

in both cases intended to be assembled in the mobile-bearing knee joint prosthesis (3.4) by the user.

Note 2 to entry: The mobile-bearing component is usually a sub-component of the tibial component (3.11),

supported by the tibial tray (3.13).

Note 3 to entry: The mobile-bearing component can also be referred to as the meniscal component.

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ISO/FDIS 21536:2023(E)

[SOURCE: ISO 7207-1:2007, 3.2.10, modified — Note 1 to entry has been replaced and Notes 2 and 3 to

entry have been added.]
3.4
mobile-bearing knee joint prosthesis

total knee joint prosthesis (3.14) or uni-compartmental knee joint prosthesis (3.16) which allows relative

motion between the mobile-bearing component (3.3) and both the femoral component (3.1) and the tibial

tray (3.13)

[SOURCE: ISO 7207-1:2007, 3.1.6, modified — "knee joint prosthesis" has been added after "total" in the

definition and Note 1 to entry has been deleted.]
3.5
partial knee joint prosthesis
partial knee joint replacement

uni-compartmental knee joint prosthesis (3.16) or a set of components used to replace the femoral and

tibial articulating surfaces in the medial compartment of a knee joint and also the patellar and femoral

articulating surfaces in the patella­femoral compartment

Note 1 to entry: Implants which are intended to repair a cartilage focal defect(s) or to be used for a surgical

procedure like mosaicplasty are not partial knee joint prostheses for the purposes of this document.

3.6
patellar component

component of a total knee joint prosthesis (3.14) or partial knee joint prosthesis (3.5) or patella­femoral

knee joint prosthesis which is used to replace the articulating surface of the patella

Note 1 to entry: Patellar components can be monobloc or modular.
3.7
patellar tray

sub­component of a modular patellar component (3.6) of a total knee joint prosthesis (3.14) used to

support and secure the patellar insert
[SOURCE: ISO 7207-1:2007, 3.2.14]
3.8
posterior stabilized tibial insert

tibial insert (3.12) with a centre post protruding superiorly or some other mechanism which interfaces

with the femoral component (3.1) to restrict anterior translation of the femoral component (3.1) when

the knee is in flexion

Note 1 to entry: The portion of the femoral component (3.1) interfacing with the tibial insert centre post is

sometimes referred to as the “cam”.
3.9
reference implant

legally-marketed implant which, when compared to the implant under evaluation, satisfies both of the

following conditions:

a) it has the same intended use, similar materials and a similar design with regard to the specific

dimensional or performance criteria under evaluation to address the same clinical and technical

requirements, and

b) there is evidence of successful clinical use in sufficient numbers; for a sufficient period of time; and,

at a minimum, without known or reasonably-known evidence of design or performance-related

recalls with regard to the specific dimensional or performance criteria under evaluation

Note 1 to entry: The term “reference” is not intended to imply that the implant under evaluation and the

reference implant are “equivalent” or that the reference implant is a “predicate” implant. This is because for some

regulatory authorities, the terms “equivalent” and “predicate” have a meaning which is beyond that intended by

the term “reference” as used in this document.
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ISO/FDIS 21536:2023(E)

Note 2 to entry: A reference implant is the comparison implant for dimensional or performance parameter(s)

under evaluation. Other characteristics of the reference implant shall be considered in order for the comparison

to be suitable, as in some situations there can be cross-effects. Ideally, for the majority of dimensional and

performance parameters, a single reference implant should be used for comparison to the implant under

evaluation. However, more than one reference implant may be used for comparison purposes, with adequate

scientific and clinical justification.

Note 3 to entry: Some regulatory authorities require that a reference implant is one that is legally marketed in

their own country or jurisdiction. This fact can be taken into account when selecting a reference implant for the

purposes of this document.

Note 4 to entry: There is no agreed upon interpretation for what constitutes “sufficient numbers” or a “sufficient

period of time” in the above definition. Typically, a determination of what constitutes “sufficient numbers” and a

“sufficient period of time” is demonstrated by using statistical methods and clinical judgement in the evaluation

of implant performance.

Note 5 to entry: A justification for a “similar material” may include information that although the materials are

not the same, the material(s) used for the implant under evaluation can be shown to perform similarly with

regard to the test or its underlying clinical concern.

Note 6 to entry: Examples of design features that can be taken into consideration when evaluating whether an

implant has a ‘similar design’ to the implant under evaluation include means of fixation, modularity, constraint,

key dimensions and shape, processing, surface topography, surface treatment, etc. A justification for a “similar

design” therefore may include information that although the designs are not the same, the design of the implant

under evaluation can be shown to perform similarly with regard to the test or its underlying clinical concern.

Note 7 to entry: The manufacturer is responsible for identifying the reference implant(s) in accordance with the

regulatory requirements in the jurisdictions where the implant under evaluation is to be marketed.

3.10
sufficient and safe clinical use

clinical use of a legally-marketed implant in sufficient numbers, for a sufficient period of time and, at a

minimum, without known or reasonably-known evidence of design or performance-related recalls

Note 1 to entry: There is no agreed interpretation for what constitutes “sufficient numbers” or “sufficient period

of time” in the above definition. Typically, these are demonstrated by using statistical methods and clinical

judgement in the evaluation of implant performance.

Note 2 to entry: Some regulatory authorities require that a legally-marketed implant is one which is legally

marketed in their country or jurisdiction.

Note 3 to entry: For a legally-marketed system of knee replacement implants, there can be evidence to

demonstrate sufficient and safe clinical use for some parts of the system (e.g. some components and some sizes)

but not for others. For those parts of the system for which there is sufficient evidence, the requirements of this

document relating to design and testing shall not apply. For those parts of the system for which there is not

sufficient evidence to demonstrate sufficient and safe clinical use the requirements of this document relating to

design and testing shall apply.

Note 4 to entry: The manufacturer is responsible for identifying the implant with sufficient and safe clinical use

...

ISO/FDIS 21536
ISO/TC 150/SC 4
Secretariat: BSI
Date: 2023-02-22
Non-active surgical implants — Joint replacement implants —
Specific requirements for knee-joint replacement implants

Implants chirurgicaux non actifs — Implants de remplacement d'articulation — Exigences spécifiques

relatives aux implants de remplacement de l'articulation du genou
FDIS stage
© ISO 2023 – All rights reserved
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ISO/DISFDIS 21536:20212023(E)
© ISO 2023

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: + 41 22 749 01 11
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2023 – All rights reserved
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ISO/FDIS 21536:20212023(E)
Contents Page

Foreword ............................................................................................................................................................................................. v

Introduction ......................................................................................................................................................................................vi i

1 Scope ....................................................................................................................................................................................... 1

2 Normative references ....................................................................................................................................................... 1

3 Terms and definitions ...................................................................................................................................................... 2

4 Intended performance ..................................................................................................................................................... 6

5 Design attributes ................................................................................................................................................................ 7

5.1 General ................................................................................................................................................................................... 7

5.2 Tolerances and dimensions ........................................................................................................................................... 8

5.2.1 Tolerances and dimensions of taper connections ........................................................................................... 8

5.2.2 Surface finish of non-articulating regions of knee joint components ...................................................... 8

5.2.3 Surface finish of articulating surfaces of knee joint components ............................................................. 8

5.3 Thickness of knee joint components .......................................................................................................................... 8

5.3.1 General ............................................................................................................................................................................... 8

5.3.2 Thickness of UHMWPE in tibial inserts, monobloc tibial components, mobile-bearing

components, patella inserts and monobloc patellar components ............................................................................... 9

5.3.3 Thickness of metal and ceramic in femoral components, tibial trays and patellar trays ................ 9

6 Materials ............................................................................................................................................................................. 10

7 Design evaluation ............................................................................................................................................................ 10

7.1 General ................................................................................................................................................................................ 10

7.2 Pre-clinical evaluation .................................................................................................................................................. 10

7.2.1 General ............................................................................................................................................................................ 10

7.2.2 Test methods and performance requirements .............................................................................................. 12

7.3 Clinical investigation ..................................................................................................................................................... 19

7.4 Post market surveillance ............................................................................................................................................. 19

8 Manufacture ...................................................................................................................................................................... 19

9 Sterilization ....................................................................................................................................................................... 19

10 Packaging ........................................................................................................................................................................... 19

11 Information to be supplied by the manufacturer .............................................................................................. 19

11.1 General ................................................................................................................................................................................ 19

11.2 Product type and dimensions .................................................................................................................................... 20

11.3 Constructional and functional compatibility of components ....................................................................... 20

11.4 Marking ............................................................................................................................................................................... 20

11.5 Information for the patient ......................................................................................................................................... 20

11.6 Electronic instructions for use .................................................................................................................................. 20

Annex A (informative) Evaluation of the range of relative angular motion of components of fully

constrained total knee joint replacement implants ........................................................................................................ 21

Annex ZA (informative) Relationship between this European standard and the General Safety and

Performance Requirements of Regulation (EU) 2017/745 aimed to be covered .............................................. 22

© ISO 2023 – All rights reserved iii
© ISO 2021 – All rights reserved
iii
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ISO/DISFDIS 21536:20212023(E)

Bibliography .................................................................................................................................................................................... 26

iv © ISO 2023 – All rights reserved
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ISO/FDIS 21536:20212023(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 of 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

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, in collaboration with the European Committee for Standardization

(CEN) Technical Committee CEN/TC 285, Non-active surgical implants, in accordance with the Agreement

on technical cooperation between ISO and CEN (Vienna Agreement).

This third edition cancels and replaces the second edition (ISO 21536:2007), which has been technically

revised. It also incorporates the Amendment ISO 21536:2007/Amd 1:2014.

This third edition is a major revision with many added requirements. The main changes are as follows:

— 1 Scope

— The scope ishas been expanded to specify more precisely the knee joint replacement types which are

the subject of this document. Also, the scope now clarifies the requirements for implants which have

been legally marketed and for which there is a history of sufficient and safe clinical use.

— 2 Normative references

— The number of normative references has been expanded, including the addition of several ASTM

standards.
— 3 Terms and definitions

— Several new definitions arehave been added, including: a) maximum claimed flexion, b) mobile-

bearing component, c) mobile-bearing knee joint prosthesis, d) partial knee joint prosthesis and

partial knee joint replacement, e) posterior stabilized tibial insert, f) reference implant, g) sufficient

and safe clinical use, h) tibial insert, i) total knee joint prosthesis and total knee joint replacement,

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ISO/DISFDIS 21536:20212023(E)

j)ultra-high molecular weight polyethylene and UHMWPE, uni-compartmental knee joint

replacement and UKR, k) UHMWPE and l) worst case.
— 5 Design attributes

The design attributes to be taken into account arehave been specified in Clause 5.

— . The requirements for the thickness of various knee joint components made from plastic, metal and

ceramic have been expanded.
— 7.2.1 General

— Several new general requirements arehave been added in 7.2.1. These new requirements a), which

specify
a) the circumstances when a test can be omitted, b) specify that
b) the testing of the worst case shall be tested and c) specify ,

a)c) the processes to be followed when no performance requirement has been specified, and

b)d) d) specify the processes to be followed when a performance requirement has been

specified but has not been met.
— 7.2.2 Pre-clinical evaluation

— The number of pre-clinical evaluations (bench tests) to be performed ishas been greatly increased in

7.2.2.. For some of the tests, a performance requirement ishas been specified. For some of the tests

no performance requirement ishas been specified and, in these cases, a new requirement has been

added, namely the requirement to demonstrate that the performance of the implant under evaluation

is the same or better than that of a reference implant. If no reference implant exists, a sequence of

alternative options ishas been specified. These alternative options are also available in the case where

there is a performance requirement, which is not met by the implant being tested.

— 7.3 Clinical investigation

— A new clinical investigation subclause ishas been added in 7.3, with several requirements which

specify the circumstances in which a clinical investigation can be required.
— 7.4 Post market surveillance

A new post-market surveillance subclause ishas been added in 7.4,, which references the

requirements in ISO 21534:2007, 7.4.
— — 11.4 Marking.
— Several new marking requirements arehave been specified in 11.4..
— 11.6 Electronic instructions for use

— A note ishas been added in 11.6 which states that in some jurisdictions there is the option to provide

the instructions for use in electronic instead of paper format.

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.
Field Code Changed
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ISO/FDIS 21536:20212023(E)
Introduction

There are three levels of standards dealing with non-active surgical implants. These are as follows, with

level 1 being the highest:

— — level 1: general requirements for non-active surgical implants and instrumentation used in

association with implants;

— — level 2: particular requirements for families of non-active surgical implants;

— — level 3: specific requirements for types of non-active surgical implant.

This document is a level 3 standard and contains requirements applying specifically to knee joint

replacements.

The level 1 standard, ISO 14630, contains requirements that apply to all non-active surgical implants. It

also indicates that there are additional requirements in the level 2 and level 3 standards.

The level 2 standards apply to more restricted sets or families of implants such as those designed for use

in osteosynthesis, cardiovascular surgery or joint replacement. For joint replacement implants, the level

2 standard is ISO 21534.

To address all requirements, it is recommended that a standard of the lowest available level be consulted

first.
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ISO/FDIS 21536:2023(E)
Non-active surgical implants — Joint replacement implants —
Specific requirements for knee-joint replacement implants
1 Scope

This document specifies requirements for knee-joint replacement implants. Regarding safety, this

document specifies requirements for intended performance, design attributes, materials, design

evaluation, manufacture, sterilization, packaging, information supplied by the manufacturer and methods

of test.

This document applies to both total and partial knee joint replacement implants. It applies to these

replacements both with and without the replacement of the patella-femoral joint. It applies to

components made of metallic and non-metallic materials.

This document applies to a wide variety of knee replacement implants, but for some specific knee

replacement implant types, some considerations, not specifically covered in this document, can be

applicable. Further details are given in 7.2.1.27.2.1.2..

The requirements which are specified in this document are not intended to require the re-design or re-

testing of implants which have been legally marketed and for which there is a history of sufficient and

safe clinical use. For such implants, compliance with this document can be demonstrated by providing

evidence of the implant’s sufficient and safe clinical use.
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 5834-1, Implants for surgery — Ultra-high-molecular-weight polyethylene — Part 1: Powder form

ISO 7207--1:2007, Implants for surgery — Components for partial and total knee joint prostheses — Part

1: Classification, definitions and designation of dimensions

ISO 7207--2, Implants for surgery — Components for partial and total knee joint prostheses — Part 2:

Articulating surfaces made of metal, ceramic and plastics materials

ISO 10993-1, Biological evaluation of medical devices –— Part 1: Evaluation and testing within a risk

management process

ISO 14243--1, Implants for surgery — Wear of total knee-joint prostheses — Part 1: Loading and

displacement parameters for wear-testing machines with load control and corresponding environmental

conditions for test

ISO 14243--2, Implants for surgery — Wear of total knee-joint prostheses — Part 2: Methods of

measurement

ISO 14243--3, Implants for surgery — Wear of total knee-joint prostheses — Part 3: Loading and

displacement parameters for wear-testing machines with displacement control and corresponding

environmental conditions for test

ISO 14243--5, Implants for surgery — Wear of total knee prostheses — Part 5: Durability performance of

the patellofemoral joint
ISO 14630, Non-active surgical implants — General requirements

ISO 14879--1, Implants for surgery — Total knee-joint prostheses — Part 1: Determination of endurance

properties of knee tibial trays

ISO 21534:2007, Non-active surgical implants — Joint replacement implants — Particular requirements

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ISO/FDIS 21536:2023(E)

ASTM F648, Standard Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated

Form for Surgical Implants

ASTM F1223, Standard Test Method for Determination of Total Knee Replacement Constraint

ASTM F2722, Standard Practice for Evaluating Mobile Bearing Knee Tibial Baseplate Rotational Stops

ASTM F2723, Standard Test Method for Evaluating Mobile Bearing Knee Tibial Baseplate/Bearing

Resistance to Dynamic Disassociation
ASTM F2724, Standard Test Method for Evaluating Mobile Bearing Knee Dislocation

ASTM F2777, Standard Test Method for Evaluating Knee Bearing (Tibial Insert) Endurance and

Deformation Under High Flexion

ASTM F3210, Standard Test Method for Fatigue Testing of Total Knee Femoral Components under Closing

Conditions
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 14630, ISO 21534 and

ISO 7207-1 and the following apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— — ISO Online browsing platform: available fromat https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1
femoral component

component of a total knee joint prosthesis (3.14(3.14),), patella-femoral knee joint prosthesis, or uni-

compartmental knee joint prosthesis (3.16(3.16)) intended to be secured to the femur to replace its

articulating surface(s)

[SOURCE: ISO 7207-1:2007, 3.2.3, modified – text has been added and NOTE has been deleted]

3.2
maximum claimed flexion

highest amount of flexion the total knee joint prosthesis (3.14(3.14)) or uni-compartmental knee joint

prosthesis (3.16(3.16)) can achieve as claimed by the manufacturer based on the requirements defined in

7.2.2.117.2.2.11

Note 1 to entry: A higher amount of flexion than the maximum claimed flexion can exist based on computer aided

design (CAD) or implant shape considerations.
3.3
mobile-bearing component

component of a total or uni-compartmental mobile-bearing knee joint prosthesis (3.4(3.4)) which

articulates with both the femoral component (3.1(3.1)) and the tibial tray (3.13(3.13))

[SOURCE: ISO 7207-1:2007, 3.2.10, modified – NOTE has been deleted]

Note 1 to entry: The mobile-bearing component can be manufactured as one component or a set of components, in

both cases intended to be assembled in the mobile-bearing knee joint prosthesis (3.4(3.4)) by the user.

Note 2 to entry: The mobile-bearing component is usually a sub-component of the tibial component (3.11(3.11),),

supported by the tibial tray (3.13(3.13).).

Note 3 to entry: The mobile-bearing component can also be referred to as the meniscal component.

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[SOURCE: ISO 7207-1:2007, 3.2.10, modified — Note 1 to entry has been replaced and Notes 2 and 3 to

entry have been added.]
3.4
mobile-bearing knee joint prosthesis

total knee joint prosthesis (3.14(3.14)) or uni-compartmental knee joint prosthesis (3.16(3.16)) which

allows relative motion between the mobile-bearing component (3.3(3.3)) and both the femoral component

(3.1(3.1)) and the tibial tray (3.13(3.13))

[SOURCE: ISO 7207-1:2007, 3.1.6, modified – text— "knee joint prosthesis" has been added after "total"

in the definition and NOTENote 1 to entry has been deleted].]
3.5
partial knee joint prosthesis
partial knee joint replacement

either a uni-compartmental knee joint prosthesis (3.16(3.16)) or a set of components used to replace the

femoral and tibial articulating surfaces in the medial compartment of a knee joint and also the patellar

and femoral articulating surfaces in the patella-femoral compartment

Note 1 to entry: Implants which are intended to repair a cartilage focal defect(s) or to be used for a surgical

procedure like mosaicplasty are not partial knee joint prostheses for the purposes of this document.

3.6
patellar component

component of a total knee joint prosthesis (3.14(3.14)) or partial knee joint prosthesis (3.5(3.5)) or patella-

femoral knee joint prosthesis which is used to replace the articulating surface of the patella

Note 1 to entry: Patellar components can be monobloc or modular.

[SOURCE: ISO 7207-1:2007, 3.2.13, modified – text has been added and NOTE has been modified to delete reference

to Figure]
3.7
patellar tray

sub-component of a modular patellar component (3.6(3.6)) of a total knee joint prosthesis (3.14(3.14))

used to support and secure the patellar insert
[SOURCE: ISO 7207-1:2007, 3.2.14]
3.8
posterior stabilized tibial insert

tibial insert (3.12(3.12)) with a centre post protruding superiorly or some other mechanism which

interfaces with the femoral component (3.1(3.1)) to restrict anterior translation of the femoral component

(3.1(3.1)) when the knee is in flexion

Note 1 to entry: The portion of the femoral component (3.1(3.1)) interfacing with the tibial insert (3.12) centre post

is sometimes referred to as the “cam”.
3.9
reference implant

legally-marketed implant which, when compared to the implant under evaluation, satisfies both of the

following conditions:

a) a) it has the same intended use, similar materials and a similar design with regard to the specific

dimensional or performance criteria under evaluation to address the same clinical and technical

requirements, and
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ISO/FDIS 21536:2023(E)

b) b) there is evidence of successful clinical use in sufficient numbers; for a sufficient period of time;

and, at a minimum, without known or reasonably-known evidence of design or performance-related

recalls with regard to the specific dimensional or performance criteria under evaluation

Note 1 to entry: The term “reference” is not intended to imply that the implant under evaluation and the reference

implant are “equivalent” or that the reference implant is a “predicate” implant. This is because for some regulatory

authorities, the terms “equivalent” and “predicate” have a meaning, which is beyond that intended by the term

“reference” as used in this document.

Note 2 to entry: A reference implant is the comparison implant for dimensional or performance parameter(s) under

evaluation. Other characteristics of the reference implant shall be considered in order for the comparison to be

suitable, as in some situations there can be cross-effects. Ideally, for the majority of dimensional and performance

parameters, a single reference implant should be used for comparison to the implant under evaluation. However,

more than one reference implant may be used for comparison purposes, with adequate scientific and clinical

justification.

Note 3 to entry: Some regulatory authorities require that a reference implant is one that is legally marketed in their

own country or jurisdiction. This fact can be taken into account when selecting a reference implant for the purposes

of this document.

Note 4 to entry: There is no agreed upon interpretation for what constitutes “sufficient numbers” or a “sufficient

period of time” in the above definition. Typically, a determination of what constitutes “sufficient numbers” and a

“sufficient period of time” is demonstrated by using statistical methods and clinical judgement in the evaluation of

implant performance.

Note 5 to entry: A justification for a “similar material” may include information that although the materials are not

the same, the material(s) used for the implant under evaluation can be shown to perform similarly with regard to

the test or its underlying clinical concern.

Note 6 to entry: Examples of design features that can be taken into consideration when evaluating whether an

implant has a ‘similar design’ to the implant under evaluation include means of fixation, modularity, constraint, key

dimensions and shape, processing, surface topography, surface treatment, etc. A justification for a “similar design”

therefore may include information that although the designs are not the same, the design of the implant under

evaluation can be shown to perform similarly with regard to the test or its underlying clinical concern.

Note 7 to entry: The manufacturer is responsible for identifying the reference implant(s) in accordance with the

regulatory requirements in the jurisdictions where the implant under evaluation is to be marketed.

3.10
sufficient and safe clinical use

clinical use of a legally-marketed implant in sufficient numbers, for a sufficient period of time and, at a

minimum, without known or reasonably-known evidence of design or performance-related recalls

Note 1 to entry: There is no agreed interpretation for what constitutes “sufficient numbers” or “sufficient period of

time” in the above definition. Typically, these are demonstrated by using statistical methods and clinical judgement

in the evaluation of implant performance.

Note 2 to entry: Some regulatory authorities require that a legally-marketed implant is one which is legally

marketed in their country or jurisdiction.

Note 3 to entry: For a legally-marketed system of knee replacement implants, there can be evidence to demonstrate

sufficient and safe clinical use for some parts of the system (e.g. some components and some sizes) but not for

others. For those parts of the system for which there is sufficient evidence, the requirements of this document

relating to design and testing shall not apply. For those parts of the system for which there is not sufficient evidence

to demonstrate sufficient and safe clinical use the requirements of this document relating to design and testing shall

apply.

Note 4 to entry: The manufacturer is responsible for identifying the implant with sufficient and safe clinical use in

accordance with the regulatory requirements in the jurisdictions where the implant is to be marketed.

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3.11
tibial component

component of a total knee joint prosthesis (3.14(3.14)) or uni-compartmental knee joint prosthesis

(3.16(3.16)) intended to be secured to the tibia to replace its articulating surface(s)

Note 1 to entry: Tibial components can be monobloc or modular. When modular the tibial component usually

consists either of a tibial insert (3.12(3.12)) or a mobile-bearing component (3.3(3.3);); and a tibial tray (3.13(3.13).).

[SOURCE: ISO 7207-1:2007, 3.2.5, modified - text— "knee joint prosthesis" has been added and NOTE has

been modified byafter "total" in the addition of thedefinition and a second sentence above]has been

added to Note 1 to entry.]
3.12
tibial insert

sub-component of a modular tibial component (3.11(3.11)) of a total knee joint prosthesis (3.14(3.14)) or

uni-compartmental knee joint prosthesis (3.16(3.16)) which is attached to the tibial tray (3.13(3.13)) and

which articulates with the femoral component (3.
...