The different spatial sideway of geodes in the same femoral head, their number, dimensions, origin, suggested to us the present document. Before now, it has already been analysed cystic hollows in primary arthrosis. Actually on our study, we relate the outcomes regarding the same phenomenon in rheumatoid arthritis.

Materials and methods. We choose femoral head previously scheduled, considering the same pre-operatory radiographic weightiness diagrams. These were undergone to a parallel and vertical planes cut among them. On three millimetres thickness slices, thanks to constant radiographic enlargement by semiautomatic images analyzator, we detected the number, site and dimensions of geodes. The data obtained, formed into a groups for quadrant (limited by two orthogonal planes crossing the centre of rotation), has been treated by statistical analysis (Anova and t-test).

Results and conclusions. According to preliminary results, it would turn out just one difference between the geodes observed in primary arthrosis and in hip arthrosis secondary to rheumatoid arthritis. This difference it consists in the dimension of cystic hollows that are bigger in rheumatoid arthritis according to the phisiopathology and anatomopathologic particularities.