Aims. Unipolar and bipolar femur head replacement in the cases of proximal femur fractures is considered one of the most common surgical procedures. But the most often post-op complication is the acetabulum cartilage erosion. The aim of this research was to estimate the speed of cartilage erosion two mentioned above surgical operations. Methods. The follow-up of 75 patients after unipolar and 62 after bipolar in the period of 24–30 (average 25.6) months post-op was performed. The average age was 78 + 13,5 years. To increase the correctness of measurement we have used the method of computer-assistant evaluation of X-ray þlms, proposed by the author. X-ray þlms were scanned. After it the special virtual ruler was placed to the scanogram to measure needed data. The presence of the artiþcial joint in the pelvis area with known sizes of its components have given the opportunity to þt the virtual ruler according to the size of artiþcial joint (for example Ð prosthesis head diameter). Results. To get the cartilage wear speed we estimated þrst the height of the cartilage before the surgery. It was 4.55 mm in average and depended on the level of degenerative processes in the hip. The average follow-up period was 25.6 months. In this period both groups have shown the wear of the acetabular cartilage. The average cartilage erosion speed in the þrst (unipolar) group was higher (1.3 mm in 2 years) then in the second (bipolar) Ð 0.6 mm in 2 years. The erosion speed increased in the presence of preoperative signs of degenerative processes in the hip and depended on its level. Conclusions. Mentioned above data shows that bipolar hip replacement causes less destructive processes in the acetabulum than unipolar.