ISO/TS 4549:2023

TECHNICAL ISO/TS
SPECIFICATION 4549
First edition
2023-07
Orthotics — Method for testing
the reliability of microprocessor-
controlled ankle moment units of
ankle-foot orthoses
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Designations and symbols . 2
5 Requirements . 3
5.1 General . 3
5.2 Definition of Test parameters . 3
5.2.1 General . 3
5.2.2 Test without integrated sensors . . 3
5.2.3 Example of a set of test levels . 4
5.3 Test preparation . 4
6 Set-up conditions . 5
6.1 General . 5
6.2 Coordinate system . 5
6.3 Leg dummy . 5
6.4 Loading of the leg dummy . 5
6.5 Essential properties of orthoses to test . 6
6.6 Vertical loading of the Orthoses . 6
6.7 Angular profile of the tilting plate . 6
7 Test procedure .8
7.1 Static test for motion resistance of the ankle joint dummy . 8
7.2 Cyclic test . 9
8 Test report . 9
9 Compliance .10
9.1 Compliance to motion resistance of the ankle joint dummy . 10
9.2 Compliance to cyclic test . 10
9.3 Identifier of Compliance . 10
9.3.1 General format . 11
Annex A (informative) Measurement system for the acquisition of load data of an orthosis
for the lower limbs .12
Bibliography .15
iii
Foreword
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This document was prepared by Technical Committee ISO/TC 168, Prosthetics and orthotics.
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.
iv
Introduction
Orthoses of the lower limb are used to treat a wide variety of pathologies. To partly compensate
functional deficits, orthoses are used, which provide appropriate functions. The more functionality is
provided by orthoses, the more important their functional reliability is.
Structural strength of orthoses, supporting the limb by stabilizing its joints against motion, is as
important as stabilisation of movement of joints between limb segments, when mobility is aimed in
rehabilitation.
Testing reliability of the controlled ankle moment units of orthoses, which stabilise joint movement,
requires to introduce motion into the strength test.
The reliability of microprocessor-controlled ankle moment units of orthosis, supporting the anatomical
ankle joint in plantar- and dorsiflexion motion, can be tested by repetitively loading and driving the
ankle joint in an appropriate angular and force profile, resulting in the moment profile to test.
Current technologies for acquiring loading and motion-data of orthotic ankle joints in real use are the
basis to derive test conditions, which simulate repetitive loading for the microprocessor-controlled
ankle moment units in a laboratory environment.
Orthoses of the lower limb are operating aside the leg of the orthosis user. For testing the reliability of
microprocessor-controlled ankle moment units in a laboratory test, it is essential to mimic the orthosis
user's extremity in such a way, that the orthosis shows its functional capabilities and its reliability. The
chapter “leg dummy” in this document describes essential properties of the leg dummy, mimicking the
orthosis user's leg.
Covering high loading events during intended use, to be generated by the control elements repetitively
in the test, provides a safety factor also for lower loading scenarios of less demanding pathologies.
The Osaka Electro-Communication University in Japan has developed a system of miniaturised sensors
with associated data acquisition and data analysis, which can be integrated into an ankle-foot orthosis
to measure the multi-axial loading and angular movement of orthotic ankle joints. This system has
been used by 50 ankle-foot orthosis users to explore the assessment processes for the reliability of
microprocessor-controlled ankle moment elements provided in this document.
v
TECHNICAL SPECIFICATION ISO/TS 4549:2023(E)
Orthotics — Method for testing the reliability of
microprocessor-controlled ankle moment units of ankle-
foot orthoses
1 Scope
This document specifies a method for testing the reliability of microprocessor-controlled ankle moment
units of ankle-foot orthosis, moving in plantar- and dorsiflexion direction.
This document specifies categories of locomotion profiles to be applied together with appropriate
loading profiles, to generate plantar- and dorsiflexion ankle moment loads for the microprocessor-
controlled ankle moment units. It also defines which measured outcome of the test allows to claim
compliance to this document, and how the compliance is documented in the IFU.
This document solely addresses the resistance of microprocessor-controlled ankle moment units in
motion. Geometrical constrains like end stops, where motion is stopped instead of sustaining it, can be
tested in repetitive quasi static tests instead.
A method to derive test parameters for the reliability test of microprocessor-controlled ankle moment
units is described.
This document is applicable to unilateral ankle-foot orthoses and to bilateral jointed orthoses where
either both joints are controlled or where one joint is controlled and the other is not controlled.
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 22675:2016, Prosthetics — Testing of ankle-foot devices and foot units — Requirements and test
methods
ISO 22523:2006, External limb prostheses and external orthoses — Requirements and test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
microprocessor-controlled ankle moment unit
flexing and extending element, bearing loads and generating ankle moment, located medial or lateral to
the anatomical upper ankle joint, providing or varying ankle moment when moved in the direction of
dorsiflexion and plantarflexion
3.2
passive ankle joint
flexing and extending element, located preferably medial to the ankle joint, mainly bearing loads
parallel to its plane of motion
Note 1 to entry: The passive ankle joint stabilises the controlled ankle moment unit on the opposite side of the
anatomical ankle joint with regard to forces and rotational moments, especially in frontal- and transversal plane.
3.3
load distribution ring
rigid ring located above the proximal end of the orthosis, to distribute the test force on the orthosis
upper brace and to avoid pressure spots
3.4
shank element
strait rod or tube, located in the tibia region of an anatomical leg, which transfers the load from the
dummy's knee to the dummy's foot; it also guides the load distribution ring and aligns the ring in the
transverse plane on a level, suitable to load the interface component of the orthoses parallel to the
shank element
3.5
outer shank element
ring, connected to the lower surface of the load distribution ring, which positions the upper brace of the
orthosis relative to the shank element
Note 1 to entry: The height of the ring is adapted to the height of the upper brace of the orthosis.
Note 2 to entry: The contour and compliance of the outer shank element may not stabilize the orthotic frame with
regards to its deflection in either plane.
3.6
orthotic frame
connecting element(s) which connect the upper brace of the orthosis to the ankle joint element(s)
Note 1 to entry: The frame can be designed by using side bars or by a brace structure.
3.7
leg dummy
an assembly of modified prosthetic componentry, mimicking the lower leg of the user of an orthosis in
the test setup
3.8
ankle moment measured
readout of the ankle moment value, measured with calibrated and validated sensors, which are
integrated in the orthotic systems bearing structure for studies and/or for testing or which are part of
the microprocessor-controlled ankle moment units
4 Designations and symbols
The designations and symbols of all relevant test forces and moments are listed in Table 1.
Table 1 — Designations and symbols of test forces and moments
Designation Symbol
Test force F
u
st nd
1 and 2 maximum value of pulsating test force F , F
1cmax 2cmax
Minimum moment measured M
min
Maximum moment measured M
max
5 Requirements
5.1 General
The selection of test levels and test force related to the intended use are defined by the manufacturer/
submitter with justification and documented in the test report prior testing (see Clause 8).
In order to claim compliance with this document, all relevant settings in the specific adjustments shall
be tested and the strength requirements specified in ISO 22523:2006, 4.4 shall be met.
The selection criteria for the samples to be tested shall be in accordance with ISO 22675.
In order to test the reliability of microprocessor-controlled ankle moment units, the ankle joint of the
leg dummy shall not limit the motion of the orthotic joint(s) under load. Suitability of an ankle joint in
the leg dummy shall be demonstrated in the static test for motion-resistance of the ankle joint dummy,
defined in 7.1 before conducting the cyclic test.
5.2 Definition of Test parameters
5.2.1 General
Depending on the intended use, the manufacturer/submitter provides sufficient information to derive
the appropriate test parameters by defining angular range, loading parameters and cycle number
to generate the ankle moment loading of the microprocessor-controlled ankle moment unit in the
laboratory test for the test lab. This information can be gained with orthoses which are equipped with
calibrated and validated sensors, worn by the intended user group, performing the intended use in a
representative size of the user group. The orthoses used to acquire the data
...