Parameters of unimplanted and explanted surfaces of Weller endoprosthesis stems.

40 samples of stem surfaces of the Weller endoprosthesis of hip joint removed because of aseptic loosening were tested. The patients between the ages of 61 and 87 were examined and the exploitation time of endoprosthesis ranged from 1 to 20 years. The material analysed was as follows: I group - exploitation 1-3 years (5 surfaces), II group - exploitation 5-8 years (11 surfaces), III group - exploitation 10-14 years (14 surfaces), and IV group - exploitation 16-20 years (10 surfaces). Additionally group 0 covered 4 unexploited endoprostheses. We analysed the 2-4 mm2 surfaces of the Weller endoprosthesis stems, with the scan velocity of 500 mum/s. A decrease in stem amplitude parameters means some increase in stem microdisplacements in relation to cement. During the first three years, the decrease in the roughness of endoprosthesis surface was larger compared with that in further exploitation period. In the case of unexploited surfaces of stems, the values of fractal dimension are lower (2.34). During exploitation time the Sfd parameter decreases negligibly (2.28-2.24).