ISO/TS 16955:2016

Overview

ISO/TS 16955:2016 is a Technical Specification from ISO/TC 168 that defines quantitative test methods to evaluate key performance indicators (KPIs) of prosthetic ankle–foot devices and foot units. It specifies test setups, sensor configurations and derived parameters (stiffness, lever arm, effective foot length, torsional and frontal-plane characteristics, energy, full-contact motion, etc.). The document describes how to record force, displacement, moment and angular data and how to calculate metrics that characterize device mechanical behaviour. Note: this TS defines measurement methods only; correlation of these metrics to user benefit is addressed separately.

Key topics and requirements

• Scope: methods to quantify mechanical performance of ankle–foot prostheses (jointed and unjointed with elastic elements).
• Mandatory quantification: to claim compliance all parameters in the TS must be measured and the strength requirements of ISO 22523:2006 must be met.
• Test setup: use coordinate system and configurations in ISO 22675:2016; tests are defined for a 26 cm foot sized for a 70 kg amputee.
• Sensor placement: a force–moment sensor positioned above midfoot at 500 mm height; displacement and angular sensors rigidly connected to record vertical displacement and torsional angle.
• Loading profiles and limits:
  • Heel/toe: sinusoidal load to 120 % of designed max body weight (example in TS: 824 N) with loading/unloading time (1 ± 0.1) s.
  • Mid-foot: peak load 200 % (1 373 N) with plate horizontal, same timing.
  • Roll-over tests apply force over plate angles −15° to +20° with duration 600 ms ± 10 %.
• Calculated parameters include: stiffness, lever arm length and change, effective foot length/width, full contact motion, torsional stiffness and angular range, and energy (integral of force × displacement).

Applications and users

ISO/TS 16955:2016 is practical for:

• Prosthetic manufacturers - product development, design validation and comparative performance testing.
• Test laboratories - standardized measurement protocols for R&D and QA.
• Clinical researchers - objective mechanical metrics to support studies linking device mechanics to gait outcomes.
• Regulators and procurement - consistent data for specification, acceptance testing and product comparison.

Using this TS helps produce repeatable, comparable mechanical data (stiffness, roll-over, torsion, frontal response) that support better device selection, optimization and communication of device characteristics.

Related standards

• ISO 22675:2016 - test configurations and coordinate system referenced by the TS.
• ISO 22523:2006 - strength requirements that must be met.
• ISO 10328 - structural testing and test preparation guidance.