ISO 17327-1:2018
(Main)Non-active surgical implants — Implant coating — Part 1: General requirements
Non-active surgical implants — Implant coating — Part 1: General requirements
ISO 17327-1:2018 specifies general requirements for implant coatings, comprising both surface coatings and surface modifications, applied to non-active surgical implants. This document specifies requirements concerned with generic coating properties including chemical and phase compositions, surface texture, coating coverage integrity, dissolvability, coating thickness, adhesion strength, abrasion resistance, porosity and pore size, and surface wettability. ISO 17327-1:2018 is applicable to surface coatings, which are defined as layers of material with any different property than the natural surface of the substrate which are intentionally added to the substrate. ISO 17327-1:2018 is applicable to surface modifications, which are defined as intentional conversion or reconstruction of the surface of the original substrate to form a new surface material consisting of components of the substrate's own material and possibly foreign material and forming a surface layer with different properties. Since the pertinent properties of a coating and their needed level of characterization are highly dependent on the intended application of the implant, the generic nature of the general requirements in this document is not intended to either override or replace the provisions of application-specific performance standards. ISO 17327-1:2018 is not applicable to surfaces modified by texturing with the exclusive intention to change the roughness of the surface or the strength of the raw material. ISO 17327-1:2018 is not applicable to natively passivated metal surfaces. While this document is applicable to intentionally passivated metal surfaces, well-established materials passivated by conventional techniques, such as nitric acid immersion, are usually non-hazardous and can be described in a very basic manner. ISO 17327-1:2018 is not applicable to implant coatings utilizing viable tissue. ISO 17327-1:2018 is not applicable to laminates, i.e. composite materials made of multiple layers, e.g. vascular prosthesis constructed of different expanded polytetrafluoroethylene layers, except the exposed surface of the laminate, which can be an implant coating (see 3.1, note 2 to entry). ISO 17327-1:2018 is not applicable to coverings, e.g. covered stents. NOTE 1 ISO 17327-1:2018 does not contain requirements on biocompatibility. Nevertheless, this is a critical property of the device and coating and needs to be addressed during risk assessment. NOTE 2 ISO 17327-1:2018 supplements applicable non-active surgical implant standards and ISO 14630. NOTE 3 ISO 17327-1:2018 does not require that manufacturers have a quality management system in place. However, the application of a quality management system, such as that described in ISO 13485, could be appropriate to help ensure that the implant achieves its intended performance. NOTE 4 Although fully porous implants are not coatings, some of the considerations in this document can also be applied to them.
Implants chirurgicaux non actifs — Revêtement de l'implant — Partie 1: Exigences générales
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 17327-1
First edition
2018-02
Non-active surgical implants —
Implant coating —
Part 1:
General requirements
Implants chirurgicaux non actifs — Revêtement de l'implant —
Partie 1: Exigences générales
Reference number
ISO 17327-1:2018(E)
©
ISO 2018
---------------------- Page: 1 ----------------------
ISO 17327-1:2018(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2018
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, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 17327-1:2018(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 General Requirements . 4
4.1 General description of the coating . 4
4.2 Generic coating properties . 4
4.2.1 General. 4
4.2.2 Chemical composition . 5
4.2.3 Phase composition . 5
4.2.4 Surface texture . 6
4.2.5 Coating coverage integrity . 6
4.2.6 Dissolvability . 6
4.2.7 Coating thickness . 7
4.2.8 Adhesion strength . . 7
4.2.9 Abrasion resistance . 7
4.2.10 Porosity and pore size . 8
4.2.11 Surface wettability . 8
Annex A (informative) Coating technology examples . 9
Annex B (informative) Examples of intended functions of implant coatings .11
Annex C (informative) Standards with information related to coatings .12
Bibliography .14
© ISO 2018 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 17327-1:2018(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 150, Implants for surgery.
A list of all parts in the ISO 17327 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 17327-1:2018(E)
Introduction
A wide variety of coatings are applied to numerous types of non-active surgical implant substrates.
These coated implant substrates have a diversity of functionalities and intended uses and exhibit
a plurality of mechanical, physical, chemical, biological and morphological/structural properties.
Even though there are diversities among the types of coating applied to surgical implants, there are
common attributes that can be used to define, evaluate and understand these implant coatings within a
surgical implant application. This document defines general principles to be followed by manufacturers
of coatings for non-active surgical implants. As the coating can represent the direct interface of the
implant with the human body, the coating and its interface with the substrate can contribute to the
potential failure of the intended function of the implant. A coating possesses unique features, properties
and risks for its interaction with the tissue, which may not have been considered in detail in existing
standards.
The role of this document is to provide a framework of design principles and evaluation guidelines for
coatings on non-active surgical implants, hereafter referred to as implant coatings. Because similar
basic principles can be applied to different technologies for implant coatings, this is a comprehensive
document and is not limited to specific types of non-active surgical implants or to particular materials.
Accordingly, this document can be applied, yet is not restricted to, metallic, ceramic, drug and polymeric
coatings used in implants across a variety of applications.
This document provides guidance on generic coating properties and the potential methods that can be
used to assess them. This document is not intended as a performance standard and provides neither
a set of device performance criteria nor rigidly held test methods, including pass/fail criteria, as this
might result in either an unnecessary constraint on the development and use of novel implant coatings,
or a false sense of security in their general use for implants.
In some cases, national and international standards are available and can be used to show compliance
with essential requirements for specific coating/substrate combinations, and these standards are
referenced in Annex C. Beyond these available application and performance standards, this document
provides general guidance and generic principles for the evaluation of non-standardized implant
coating combinations.
© ISO 2018 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 17327-1:2018(E)
Non-active surgical implants — Implant coating —
Part 1:
General requirements
1 Scope
This document specifies general requirements for implant coatings, comprising both surface
coatings and surface modifications, applied to non-active surgical implants. This document specifies
requirements concerned with generic coating properties including chemical and phase compositions,
surface texture, coating coverage integrity, dissolvability, coating thickness, adhesion strength,
abrasion resistance, porosity and pore size, and surface wettability.
This document is applicable to surface coatings, which are defined as layers of material with any
different property than the natural surface of the substrate which are intentionally added to the
substrate.
This document is applicable to surface modifications, which are defined as intentional conversion or
reconstruction of the surface of the original substrate to form a new surface material consisting of
components of the substrate’s own material and possibly foreign material and forming a surface layer
with different properties.
Since the pertinent properties of a coating and their needed level of characterization are highly
dependent on the intended application of the implant, the generic nature of the general requirements
in this document is not intended to either override or replace the provisions of application-specific
performance standards.
This document is not applicable to surfaces modified by texturing with the exclusive intention to change
the roughness of the surface or the strength of the raw material.
This document is not applicable to natively passivated metal surfaces. While this document is applicable
to intentionally passivated metal surfaces, well-established materials passivated by conventional
techniques, such as nitric acid immersion, are usually non-hazardous and can be described in a very
basic manner.
This document is not applicable to implant coatings utilizing viable tissue.
This document is not applicable to laminates, i.e. composite materials made of multiple layers, e.g.
vascular prosthesis constructed of different expanded polytetrafluoroethylene layers, except the
exposed surface of the laminate, which can be an implant coating (see 3.1, note 2 to entry).
This document is not applicable to coverings, e.g. covered stents.
NOTE 1 This document does not contain requirements on biocompatibility. Nevertheless, this is a critical
property of the device and coating and needs to be addressed during risk assessment.
NOTE 2 This document supplements applicable non-active surgical implant standards and ISO 14630.
NOTE 3 This document does not require that manufacturers have a quality management system in place.
However, the application of a quality management system, such as that described in ISO 13485, could be
appropriate to help ensure that the implant achieves its intended performance.
NOTE 4 Although fully porous implants are not coatings, some of the considerations in this document can also
be applied to them.
© ISO 2018 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 17327-1:2018(E)
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 14630, Non-active surgical implants — General requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14630 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www.el ectropedia. org/
— ISO Online browsing platform: available at https:// www. iso. org/obp
3.1
implant coating
surface coating (3.2) or surface modification (3.3)
Note 1 to entry: Implant coating is considered a constituent of an implant.
Note 2 to entry: A laminate, i.e. a composite material made of multiple layers of the same or different materials
with the same or different internal structures assembled sandwich-like and bonded by heat, pressure, welding,
soldering or adhesives, is not in itself considered an implant coating. But the exposed surface of the laminate can
be an implant coating.
Note 3 to entry: A covering, for example additional material (e.g. a graft) added to a structure (e.g. a stent)
specifically to bridge elements of the structure for the sole purpose of reducing the permeability of the structure,
is not considered an implant coating.
3.2
surface coating
layer of material with any different property than the natural surface of the substrate that is
intentionally added to the substrate
Note 1 to entry: The coating can partially or fully cover the substrate surface.
Note 2 to entry: The term includes surface coatings created as a result of additive manufacturing.
3.3
surface modification
intentional conversion or reconstruction of the surface of the original substrate to form a new surface
material consisting of components of the substrate’s own material and possibly foreign material and
forming a surface layer with different properties
3.4
coating property
measurable characteristic of a coating
Note 1 to entry: A coating property can for example be mechanical, physical, chemical or
morphological/microstructural in nature.
Note 2 to entry: In multi-layered coatings, one or more characteristics are designed to change along the coating
depth with one or more corresponding interfaces. These characteristics are also considered coating properties.
Note 3 to entry: In gradient coatings, one or more characteristics are designed to change (increase or decrease
in magnitude of a particular property) along the coating depth without interfaces. These characteristics are also
considered coating properties.
2 © ISO 2018 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 17327-1:2018(E)
3.5
generic coating property
coating property (3.4) generally of importance for most types of coatings
3.6
pertinent property
coating property (3.4) relevant to the safety and/or efficacy of the device when used in its intended
application
3.7
abrasion resistance
resistance to mechanical damage exhibited by articulating against a surface
3.8
adhesion strength
load per unit area required to separate the coating from the substrate
3.9
chemical composition
type and ratio of the chemical constituents
Note 1 to entry: If the coating comprises multiple substances, the chemical composition of each substance and
the ratio of these substances might also be important. The latter can be expressed as molar fraction, volume
fraction, mass fraction, molality, molarity or normality.
3.10
coverage integrity
absence of significant coverage defects
3.11
phase
homogeneous portion of an implant coating that has uniform physical and chemical
properties
Note 1 to entry: Phases have distinct physical (e.g. according to their crystalline structure) or chemical (e.g.
according to their chemical composition) properties and are separated from each other by definite phase
boundaries.
[37]
[SOURCE: Callister Jr., W.D.; Rethwisch D.G. “Materials Science and Engineering: An Introduction” .
Chapter 9.3 “Phases”, modified — replaced “system” with “implant coating” and “characteristics” with
“properties”, Note 1 to entry has been added.]
3.12
phase composition
description of the various phases and their proportions
3.13
pore size
dimensional measure of void space
Note 1 to entry: Depending upon the specific description, pore size can be described as a length, an area or a
volume. Pore size can also describe either singular voids or aggregates of void spaces.
3.14
porosity
volume fraction of voids/pores in the total coating volume consisting of solid and
void components
3.15
dissolvability
ability of a solid, liquid or gas to be dissolved in a solvent without any chemical reaction
© ISO 2018 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 17327-1:2018(E)
3.16
solubility
maximum mass of a solute that can be dissolved in a unit volume of solution measured under equilibrium
conditions
Note 1 to entry: The solubility depends on chemical composition, structure and phase composition (3.12) of the
solute and the solvent as well as on temperature, pH and pressure of the solution.
3.17
dissolution rate
change of the dissolved mass of a solute with time
3.18
surface texture
property describing the non-smooth nature of a surface
Note 1 to entry: The surface texture can for example be characterized by:
a) The fabric as a directed or ordered, isotropic or non-isotropic arrangement of surface patterns (e.g. grooves
or scratches);
b) The roughness as a measure of finely spaced surface irregularities with usually random distribution;
c) The waviness as a measure of surface irregularities with a spacing larger than that of the surface roughness
(e.g. due to machining).
3.19
surface wettability
ability of a solid surface to influence the contacting liquid to spread over that surface
3.20
thickness
distance between the substrate and the outer surface of the coating in a direction
orthogonal to the substrate
Note 1 to entry: For a multi-layer coating, the coating thickness is considered to be the total thickness of all
individual layers.
4 General Requirements
4.1 General description of the coating
An implant coating shall be described by its materials, manufacture process (for examples see
Annex A) and/or intended function (for examples see Annex B). Annex A and Annex B are only included
as information to the user of this document and provide some practical examples for manufacture
processes and intended functions respectively.
EXAMPLE PVD ceramic coating for wear reduction and as a diffusion barrier against allergenic substances.
EXAMPLE sprayed paclitaxel drug coating for restenosis reduction.
4.2 Generic coating properties
4.2.1 General
The coating and substrate constitute a system. The design and intended function of this system are
both critical for the selection of appropriate properties to evaluate or characterize.
This subclause contains a set of generic coating properties that shall be considered for evaluation or
characterization of the implant coating. Although all of the generic coating properties listed below need
to be considered, it is not necessary to test or evaluate all of these properties for each type of coating, if
4 © ISO 2018 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 17327-1:2018(E)
they are deemed not pertinent. The decision whether a generic coating property is considered pertinent
shall be done within a risk assessment process.
This document describes a set of coating properties to be considered for their potential to impact
the safety and performance of the implant when used in the intended application. It is ultimately the
responsibility of the device manufacturer to identify, control, and assess critical performance properties
of the coating as applied to a particular implant. Identification and evaluation can be facilitated by
potentially pertinent general, material, and application-specific implant standards (see Annex C for
a partial listing). Available standards, alone or in combination, can be sufficiently comprehensive to
assess a device’s safety and performance. It is within this broader and combined general, material, and
application-specific context that pertinent coating properties shall be risk-assessed for their potential
impact on implant performance. The generic coating properties provided here are not meant to be an
exhaustive list, and other properties specific to a particular coating or intended function also shall be
considered. The properties for evaluation or characterization shall be selected based on the intended
function of the implant coating. The test method to be used for coating evaluation or characterization
shall be selected to appropriately evaluate or characterize the coating according to its intended
function.
The test methods and sample preparation procedures used shall be documented in detail. Justification
shall be given for the adequacy of the method and the sample size chosen. The sample geometry shall
be in accordance with the requirements of the test method and consideration shall be given to the
substrate geometry. The substrate material of the test specimen shall be the same as the base material
of the coated implant under evaluation. The production methods of the coating shall be representative
of those used for the coating on the final implant. The test specimen shall be described including any
post-coating processes performed on it, such as cleaning, sterilization and ageing representative of the
shelf-life.
4.2.2 Chemical composition
The chemical composition and the measurable impurities of the coating shall be specified.
The chemical composition of the coating shall be characterized and documented using a methodology
most appropriate for the specific coating.
NOTE 1 The chemical compositions of different coatings can typically be characterized and documented in
e.g. elemental, molecular or oxide basis.
While deciding on the preparation technique and analysis method, the impact of the substrate material
shall be taken into account. It might be required to remove the coating appropriately before performing
the chemical analysis.
NOTE 2 ISO 10993-18 provides tests methods for chemical characterization of materials. These methods can
be used to assess the chemical composition of coatings.
4.2.3 Phase composition
Properties of coatings with specific chemical or elemental compositions can vary due to the formation
of different phases (i.e. physical states, such as crystallographic forms, amorphous states) and their
relative proportions.
The phase composition of the material is limited by but not completely defined by the chemical
composition of the coating. Phase composition of coatings is often used as a readily measured property
for specification or quality control in contrast to some of the performance related properties. In case
of crystalline solids, phase composition is ordinarily determined using X-ray diffraction analysis on a
coating separated from the substrate.
The phase composition of the coating shall be taken under consideration and it shall be decided whether
or not phase composition is a pertinent property for this specific coating.
© ISO 2018 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 17327-1:2018(E)
If phase composition is deemed pertinent, it shall be specified and verified. For verification applicable
standards given in Annex C should be used. If none of the standards given in Annex C are used, another
suitable method shall be specified and used.
If it is not deemed pertinent, no testing is required. However, a justification shall be provided to explain
why this property is not deemed pertinent.
4.2.4 Surface texture
The surface texture of a coating can be characterized by descriptive terms but shall be quantified in
terms of surface roughness parameters, if applicable.
Measurements should take into account random or orientated surfaces, as well as waviness and fabric.
The uniformity of surface texture across the coated area shall be characterized.
The surface texture of the coating shall be taken under consideration and it shall be decided whether or
not surface texture is a pertinent property for this specific coating.
If surface texture is deemed pertinent, it shall be specified and verified. For verification applicable
standards given in Annex C should be used. If none of the standards given in Annex C are used, another
suitable method shall be specified and used.
If it is not deemed pertinent, no testing is required. However, a justification shall be provided to explain
why this property is not deemed pertinent.
4.2.5 Coating coverage integrity
All coatings have some coverage defects and it is essential to determine the degree to which those
defects are detrimental to function.
NOTE Coverage defects can include cracks, deviations from uniform thickness, etc.
It shall be determined which type, size and amount (e.g. defects/unit area) of coverage defects are
pertinent to the performance of a coating. An appropriate method for detection of the pertinent
coverage defects shall be chosen and used to inspect the implant coating. The pertinent coverage defects
detected shall be specified in the form of type, size and amount (e.g. defects/unit area) as appropriate.
In this manner, the coating coverage integrity shall be specified and verified. For verification applicable
standards given in Annex C should be used. If none of the standards given in Annex C are applicable,
another suitable method shall be specified and used.
4.2.6 Dissolvability
Dissolution testing is performed in order to determine the solubility and/or the dissolution rate of
the entire coating or its components in solvents representing physiologically similar solutions. This
investigation is conducted to simulate and evaluate the degradation of the coating characterized by
the weight loss in water based buffer solutions which resemble the chemical composition and the
temperature conditions of physiological fluids.
The dissolvability of the coating shall be taken under consideration and it shall be decided whether or
not dissolvability is a pertinent property for this specific coating.
If dissolvability is deemed pertinent, it shall be specified and verified. For verification applicable
standards given in Annex C should be used. If none of the standards given in Annex C are used, another
suitable method shall be specified and used.
If it is not deemed pertinent, no testing is required. However, a justification shall be provided to explain
why this property is not deemed pertinent.
NOTE If a portion of the coating is intended to elute or dissolve over time, additional elution or release
testing will be necessary.
6 © ISO 2018 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 17327-1:2018(E)
4.2.7 Coating thickness
Coating thickness encompasses the average distance from the outer surface of the coating to the
interface between the coating and substrate, in a direction orthogonal to the substrate. A rationale shall
be provided for where the nominal interface (boundary) between well-discernible phases of the coating
and the substrate is located. The coating thickness can be determined by different methodologies
depending on the coating composition and substrate material.
NOTE 1 For some implants coating mass per area can be more pertinent than the actual coating thickness.
NOTE 2 If the coating thickness depends on the environmental conditions, e.g. the humidity, it is important to
consider the environmental conditions as well as conditioning.
The coating thickness shall be taken under consideration and it shall be decided whether or not coating
thickness is a pertinent property for this specific coating.
If coating thickness is deemed pertinent, it shall be specified and veri
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.