This study is concerned with the shape optimization of stem for the artificial hip prosthesis with unbonded cement mantle. The artificial hip prosthesis with unbonded cement mantle allows a stem to slip on cement mantle unlike the artificial hip prosthesis with bonded cement mantle. Unbonded cement mantle type has several advantages compared with bonded cement mantle type.
So, in this study, 2-dimensional axisymmetric model is developed with considering characteristics of unbonded cement mantle. And optimal shape of a stem is obtained by using feasible direction method. The optimal shape has slope of 0.15 in proximal part and maintains the width about 5mm in distal part.
In addition, Hoffman’s failure criterion is used for constraint of cement stress instead of effective uniaxial fatigue stress. The results using Hoffman’s failure criterion showed that vertical allowable loading is increased. Analysis for bonded cement mantle type is carried out and compared with unbonded cement mantle type. Vertical allowable loading for unbonded type is larger than for bonded type. And, simplified 3-dimensional analysis is carried out. The result of 3-dimensional analysis showed that bending effect and complex geometries must be studied in further research.
