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The purpose of this paper is to study the roughness effect on the fixation of taper junction components and surfaces wear in terms of taper surface design. The roughness of the femoral heads’ taper and of the femoral stems’ trunnions can influence the fretting wear of the taper junction.

It was analysed whether a microgrooved taper surface of the femoral stem trunnion improves the fixation and reduces the wear rate at the taper junction of the hip prosthesis. Two models have studied: a femoral head with a smooth tapered surface combined with a microgrooved stem trunnion and a femoral head with a smooth tapered surface combined with a trunnion that had a smooth surface of the tapered. To compare the wear evolution between these two models, a computerised finite element model of the wear was used.

The results obtained after analysis carried out during millions of loading cycles showed that the depth of the linear wear and the total material loss were higher for the femoral heads joined with microgrooved trunnions. The main conclusion of this paper is that the smooth surfaces of the taper and of the trunnions will ensure a better fixation at the taper junction, and therefore, will reduce the volumetric wear rates.

A higher fixation of the taper junction will reduce the total hip prosthesis failure and, finally, it will improve the quality and durability of modular hip prostheses.

The study aims to analyze the fretting phenomenon, manifested at the taper junctions of modular total hip prostheses (THP). Modularity of prostheses implies the micro-movement occurrence. Fractures can arise as a result of the fretting cracking of the prostheses components, affecting durability of modular THPs. Fretting corrosion is associated with the decrease in the clinical acceptance of hip modular implants.

Starting from the fretting phenomenon influence on modularity, monoblock THPs and prostheses with modular femoral head recovered from some review surgeries were investigated. Modular prostheses have a taper junction femoral head – femoral stem neck. Investigation consisted in the analysis of fretting wear and fretting corrosion, of the femoral heads’ taper and of the femoral stems’ trunnions.

The main result was that the micro-movement that provokes the fretting of the femoral head-femoral stem taper junction analyzed does not have the same direction. It is manifesting in the direction of the axis of the femoral head taper, around this axis or as a composed movement. The authors suspect that this is due to the different design of the taper. In this way, the inclination of the stem’s trunnion into the head hole has a different angular misalignment and may cause greater damages of the taper.

This result can be a starting point from the improvement of the future taper junctions design that will improve the quality, durability and modularity of THPs.

The purpose of this study was to realize finite element simulation in order to dynamically determine the area of the contact, the contact pressure and the strain energy density (identified as a damage function) for three different activities – normal walking, ascending stairs and descending stairs – that could be considered to define the level of the activity of the patient.

The finite element model uses a modern contact mechanism that includes friction between the metallic femoral condyles or femoral head (considered rigid) and the tibial polyethylene insert or acetabular cup (considering a non-linear behaviour).

For all three activities, the finite element analyses were performed, and a damage score was computed. Finally, a cumulative damage score (that accounts for all three activities) was determined, and the areas where the fatigue wear is likely to occur were identified.

A closer look at the distribution of the damage score reveals that the maximum damage is likely to occur not at the contact surface, but in the subsurface.