The Effect of Loading on the Contact Stress of UHMWPE Material for Artificial Hip Joint Bearing

Abstract

An artificial hip joint consists of several main components. The components are femoral stem, femoral head, acetabular liner and acetabular shell. As its function as a bearing, an acetabular liner is designed to reduce friction and receive the high stress. The liner is made from Ultra High Molecular Weight Polyethylene (UHMWPE) material. It is reported that the UHMWPE liner bearing is occasionally fails inside the patient’s body. This paper reports the effect of loading on the liner and predicts the liner ability in receiving the load. A finite element simulation is employed in modeling the contact system. The maximum load received by the artificial hip joint during human activities is used as input in the artificial hip joint models. The result shows that the acetabular liner receives the high stress distribution and the highest stress is located on the center of the liner. The maximum stress on the acetabular liner does not exceed the yield criteria of the UHMWPE material. It is concluded that the UHMWPE material is relatively able to carry the various loading. However, the failure of the acetabular liner can be caused by the unexpected conditions when the patient stumbles or falls down.