[Medium-term Experience with Zweymüller's Bicon Plus Cup in the Treatment of Postdysplastic Osteoarthritits of the Hip Joint.].

The authors retrospectively evaluate a group of 28 hip joints in which in 1995 and 1996 total hip replacement was performed for developmental dysplasia of the hip joint. They included in the study only patients with dysplasia of types B, C and D after Eftekhar. By means of the method after Ranawat and Pagnan they determine the ideal centre of the rotation of the hip join and the so called TAR-true acetabular region. They checked the patients in 1999 and evaluated subjective complaints, objective findings according to Harris Hip Score and x-ray findings on a radiograph of the pelvis and on the radiograph showing a 45 degrees rotation (the Judet view). In most hip joints operated on the actual centre of rotation differed from the ideal centre of rotation. Maximum difference was 18 mm. In the hip joints of type C they recorded more often a higher position of the centre of rotation (a higher placement of the cup). None of the patients was reoperated, radiographs did not show signs of aseptic loosening of the acetabular component. Zweymüller's Bicon Plus cup can be used also in cases of severe dysplasia of the hip joint. Primary stability of the implant and a good medium-term result can be achieved in most cases. The authors consider this type of implant especially suitable for patients with developmental dysplasia. Key words: total hip replacement, developmental dysplasia of the hip, Zweymuller's Bicon cup.