The clinical practice shows that the loosening of acetabular cups is more frequent than stem loosening. With standard cups, the incidence of dislocation failure is highest in the first year after arthroplasty implantation. The aim of the study was to quantitatively evaluate the implant-bone stability of a cementless acetabular cup prosthesis by using a device based on resonance frequency analysis. The evaluation of this device was done by finite element analysis and in vitro experiments. It was shown that not all the resonance frequencies can be measured by our device. The resonance frequencies vary within the range of 500–3000 Hz. The proposed power spectrum measurement gives the information about the absolute stiffness of the press-fit implant.

Stability of dental implants is measured by means of the Osstell device using a method of resonance frequency analysis. The aim of the study was to evaluate the role of direction-dependence of the Osstell transducer. For this purpose, a set of parametrical finite element analyses has been used. When rotating the transducer around the vertical axis the crucial phenomenon is the change in behavior of the system, which occurs in positions between 30 degrees and 80 degrees to the long axis of the alveolar crest. It seems from the presented results that, when measuring approximately perpendicularly to this long axis, the deviation from the ideal perpendicular position must not exceed 30 degrees. In this case, the first resonance frequency is recorded. When measuring in the approximately parallel position to the long axis of the alveolar crest, the second resonance frequency is recorded. The deviation from the ideal parallel position must not exceed 10 degrees. These values are not comparable with the previous ones.