The tribological behaviour of the dual mobility hip prosthesis in relation to impingement

Implantation of a hip prosthesis (HP) can have an extremely positive impact on quality of life, however, a number of medical problems that could limit the functioning of the prosthesis, including primary dislocation (impingement) and secondary dislocation (wear on the liner surface). A new dual mobility (DM) principle is presented based on a review of engineering strategies to reduce the risk of impingement. The DM principle was adapted to suit the Indonesian demands with respect to production, hip sizes and specific extreme movements. The final design provides a solution to overcome the limitations of the RoM within the Indonesian context. The aim of this research was to study the tribological behaviour of the new DM HP in relation to impingement based on (cross-linked) UHMWPE material and SS316L, which are available on the domestic Indonesian market, and which have passed biocompatibility tests. Furthermore, the relation between impingement was studied numerically, and a wear model was derived analytically. The result of wear model was in agreement with experimental work described in other literature. For the variation in specific wear rate and head size, the results show a large effect on the linear wear and increasing the head diameter will decrease the linear wear, respectively. The contact stress by using finite element (FE) was used to predict wear in the DM model on the contact between the head vs liner and the outer liner vs cup. For variations in the cup size, the results show that the maximum contact stress is predicted to occur for the thinner liner. The FE simulation was conducted to determine the effect of impingement on liner damage for the conventional model. The results showed that the wear on the liner surface was related to the damage of liner lip. An experimental procedure to determine the specific wear rate in a pre-clinical setting for the HP design was developed based on a pin-on-disk setup and was based on a newly developed hip-simulator setup. The results showed that the specific wear rate was above the threshold for non-cross-linked UHMWPE under dry conditions, while for bovine serum lubricated conditions was contrary.