Fatigue testing of bone cements - comparison of testing arrangements

Bone cements are a common tool for the fixation of high load bearing endoprostheses. One of the most important requirements for their save function is a sufficient strength under long-term loading conditions. Therefore, fatigue investigations are increasingly performed in addition to the usual characterization by quasistatic tests. Meanwhile, such fatigue testing methods are also discussed by the responsible ISO-committee. Three testing procedures are considered: A 4-point-bending arrangement, a pure tensile test with flat tapered specimens and a uniaxial tension/compression test with cylindrical tapered samples. Up to now, a direct comparison of these three methods has not been conducted. The aim of this study is to compare the three procedures with respect to their applicability for the assessment of the fatigue properties of bone cements. Whereas tension/compression leads to uncertainties in the interpretation of the results, it turns out that bending and pure tension deliver consistent evaluations. With respect to practicability, simplicity, and costs the bending test method which is already standardized for the quasistatic testing of bone cements is the preferable fatigue testing arrangement.