Non linear finite element analyses were performed in various configurations of stem-ball head. High stresses were found for the cases when the stem tended to penetrate less into the ball head. An upgraded design of the cone may improve the loading of the ball head to resist trauma-like loading more effectively than manipulating the ball diameter. When the surgeon needs to use small ball heads (i.e. 22 mm), the use of zirconia seems to be appropriate also. After simulating a trauma like loading of the materials, it was found that the deepness of the cone to locate the stem is of major importance for the performance of the device. Further work, considering more sizes for the cone design should be performed in order to determine an optimal depth for the cone in relation to the diameter of the ball head. Also the simulation of contacts pairs including polyethylene and CoCr is important for further research.

Four different coatings deposited using cold spray process were studied with two different powder agglomerating techniques (spray d교 and evaporated powder) and using $TiO_2$ nano-sized powders with and without a 10wt% addition of ZnO. Characterization was performed by SEM, XRD and roughness test. Also the photocatalytic effect of the coatings was evaluated. Although the change of powder preparation techniques and the addition of ZnO into $TiO_2$ did not show appreciable variations in the surface morphology and Anatase phase transformation, it did show influence on the surface roughness of the coating, the highest roughness being found in the coatings made by spray powder prepared method. Regarding the photocatalytic effect it was observed that the using the spray dry coating and the addition of ZnO are promoter of purification at higher rates.