[Biomechanical data regarding the socket-neck orientation of hip endoprosthesis].

On the basis of clinico-statistical, roentgenologic, morphological and spectral studies it is possible to draw the conclusion that the cause of the structural deformation of the bone tissue around the endoprosthesis parts and an approach of their instability is in the mechanical interaction of bone and explant. Under the influence of the biomechanical forces the socket of the endoprosthesis gradually changes its position from 45-90 degrees to 25-30 degrees. The original 25-30 degree positioning of the socket significantly decreases the moment of forces that it is subjected to and, as a rule, there is no socket displacement observed. That is why this socket positioning in the process of operation is a preferable one. But the angles of necks of the Sivash endoprosthesis and its modifications are equal to 130 degrees +/- 3 degrees and when the socket is positioned at an angle 25-30 degrees there can occur limitation of the limb abduction, the socket loosening, the structure fretting and metallosis of tissues due to the setting of the neck against the end of the insert. It is expedient to change the angle of the endoprosthesis neck to 150 degrees +/- 3 degrees and some shortening of the neck.