ISO 10328: Prosthetics – Structural testing of lower-limb prostheses – Requirements and test methods
Lower-limb prostheses do a demanding job every day. They carry load, transfer movement, withstand repeated steps and must remain reliable under defined mechanical conditions.
ISO 10328 is a 148-page summary of test methods for complete lower limb prosthesis as well as specific components such as the ankle-foot device or the knee flexion mechanism. The number of samples, static and dynamic tests, as well as performance criteria, are defined. The test loads might also serve as a reference for static and dynamic testing of osteointegration in(transfemoral) implants.
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Significance and Methodology
Real walking is mechanically complex. A lower-limb prosthesis is not exposed to just one simple force, but to a combination of compression, shear, bending and torque. ISO 10328 turns this complexity into reproducible laboratory test conditions. Static tests evaluate how a structure behaves under severe single-event loads. Cyclic tests evaluate fatigue strength under repeated loading, representing the regular load pattern of walking. The principal structural tests include static proof testing, static ultimate strength testing and cyclic testing followed by a final static load.
For components with special functions, ISO 10328 adds separate tests. Foot units are tested under heel and forefoot loading. Knee units may be tested in maximum flexion. Knee locks are tested in conditions where heel loading tends to flex the locked knee. Torsion is addressed separately as well.
Controlled Test Parameters
The standard defines the test forces, moments, offsets, angles, segment lengths and cycle counts for the applicable loading levels. These parameters are selected from the tables of ISO 10328 and depend on the component, test type and chosen loading level. For cyclic testing, this means the prosthetic structure is not simply loaded once and declared finished. It is repeatedly loaded over a prescribed number of cycles, then assessed according to the relevant performance requirements. Accuracy also matters. ISO 10328 specifies tolerances for dimensions, angles, forces, moments and test frequency. A good test is not only strong on the loading side; it is also carefully aligned, measured and documented.
Test Samples and Alignment
Test samples are normally taken from regular production. Depending on the scope of testing, they may be complete prosthetic structures, partial structures or individual components. The alignment of the sample is a central part of the method. ISO 10328 defines coordinate systems, reference planes and load application points so that the mechanical loading is reproducible. Adjustable components are set according to the required condition, often representing a worst-case alignment. This is where the test becomes very specific: the result is tied to the submitted device, the selected configuration and the alignment used in the test setup.
Ankle-Foot Devices and Foot Units
Ankle-foot devices and foot units receive dedicated attention in ISO 10328. Separate tests apply heel and forefoot loading, reflecting two important directions of load transfer during use. The selected foot size must represent the relevant worst-case loading for the device type, and the reasoning has to be documented. If a foot unit is detachable, ISO 10328 also defines how the foot and the remaining prosthetic structure are handled in the test program. This helps keep the test focused: the foot is assessed under foot-specific loading, while the rest of the structure can be assessed under the appropriate principal structural conditions.
Knee Units and Knee Locks
Knee components have their own mechanical challenges. ISO 10328 includes a separate static ultimate strength test in maximum knee flexion for knee joints and associated parts. This test represents loading situations such as kneeling or deep knee bending. Knee locks are tested separately as well. The loading condition simulates a situation where heel loading tends to flex the knee while the lock holds the joint in extension. If the lock position or alignment can be adjusted, the setup must reflect the relevant condition required by the standard.
Documentation and Compliance
ISO 10328 testing is not just about applying forces. It is also about traceability. The test submission document must identify the device, sample type, assembly details, alignment, tightening torques, relevant attachments and requested test conditions. A compliance claim must state the test loading level. It applies to the tested prosthetic assembly and alignment, not automatically to every possible configuration. If other configurations are to be covered, they must be justified within the tested range.
Testing at EndoLab
EndoLab performs structural testing of lower-limb prosthetic devices according to ISO 10328. The standard provides the framework; the test setup turns the submitted device into a clearly defined mechanical assessment. From static proof testing to cyclic fatigue testing, from ankle-foot devices to knee locks, each test is prepared, aligned, loaded and documented according to the applicable requirements of the standard.
