ISO 07206-4:2010 pdf free download – Implants for surgery一Partial and total hip joint prostheses一 Part 4: Determination of endurance properties and performance of stemmed femoral components.
Some aspects of the prior editions of ISO 7206-4 were not sufficiently described and some parts of the test method did not reflect the current test practice as shown below.
a) Test conditions for anteverted stems will result in a significant decrease of the medial-lateral bending forces. This reflects the “best case” test condition in comparison to “worst case” conditions for nonanteverted stems and will lead to test results not reflecting the high forces in the human body, because the rotated position is not considered.
b) Specific test conditions for stemmed femoral components with CT distance 120 mm are not considered.
NOTE The dimension CT is the distance between the centre of the femoral head, C, and the most distal point of the stem, T.
c) Changes in the potting level in comparison to ISO 7206-4:2002 without changes in the corresponding performance standard ISO 7206-8.
In order to overcome these disadvantages it was proposed to define the test conditions for three types of stem length, to describe the test procedure and stem axis definition particularly for anteverted stems more precisely and to harmonize the test conditions with the endurance performance of ISO 7206-8.
This edition in some respects allows more accurate and easier handling by the test laboratories and defines a clear separation of stemmed femoral components into three categories:
— stems with CT distance < 120 mm; — stems with CT distance 120 mm < CT <= 250 mm; — stems with CT distance > 250 mm.
It includes performance criteria for these components. This will lead to a higher acceptance of the test method and more reproducible test results.
4 Principle
The lower portion of the test specimen is embedded in a solid medium and a cyclic load is applied to the head of the test specimen to produce axial compression, two-plane bending and torsion until the specimen exhibits failure or until the prescribed number of cycles has been attained. The specimen is subsequently examined for defects caused by the loading regime.
NOTE Methods of examining the test specimen should be agreed between the test laboratory and the party submitting the specimen for test.
5 Materials
5.1 Embedding material
Embedding medium, i.e. a casting medium, which shall:
a) not break under the load applied during testing;
b) not exhibit excessive deformation or creep;
c) be reproducible in strength and other characteristics.
NOTE The media that appear satisfactory are acrylic bone cement (see ISO 5833), filled epoxy casting resin and liquid metal alloy. The media should have a modulus of elasticity between 2 000 N/mm2 and 6 000 N/mm2.
5.2 Fluid test medium
A 9,0 g/l solution of analytical grade sodium chloride (NaCI) in distilled or deionized water of grade 3 as specified in ISO 3696.
6 Apparatus
6.1 Testing machine, having the following characteristics:
a) ability to apply a cyclic load according to Clause 9 at a frequency of between 1 Hz and 30 Hz;
b) error in applied load: no greater than ± 2 % of maximum load as specified in ISO 4965;
c) dynamic loading waveform: sinusoidal at the primary frequency;
d) instrumentation to monitor the values of the maximum and minimum loads and the vertical deflection of the test specimen to a tolerance of ± 0,2 mm, to stop the machine if deflection exceeds a prescribed value and to record the corresponding number of cycles or the elapsed time of operation.