STAND FOR TRIBOLOGICAL STUDIES OF HIP JOINT ENDOPROSTHESIS WITH THE POSSIBILITY OF CHANGING ACETABULUM ANTEVERSION ANGLE AND HEAD ANTI TORSION ANGLE

The article presents the construction of a hip joint movement simulator intended for friction and wear studies of hip joint endoprostheses. The simulator's design enables the fixing of hip endoprosthesis components in accordance with the anatomical structure of the human hip joint. The endoprosthesis head is mounted on a special base in the lower position with a neck-shaft angle of 135°, while the acetabular cup of the endoprosthesis is mounted in the upper part of the mounting head with an inclination angle of 45°. The production of three heads (responsible for the anteversion angle of the acetabulum) and three special bases (responsible for the anti torsion angle of the head) with different fixing angles of the components of the hip joint endoprosthesis made it possible to carry out tribological tests with nine variants of alignment settings. The hip joint endoprosthesis tester is designed to simulate the following movements: flexion and extension, as well as loads occurring in the human hip joint while walking. Thanks to the use of control in the form of electronic cams, the simulator makes it possible to recreate the variable value of the force loading the friction pair as a function of the human walking cycle. The subject of friction and wear studies were hip joint endoprostheses with a head diameter of 44 mm, made of high-carbon Co28Cr6Mo alloy. For each of the nine variants of endoprosthesis component alignment settings, average friction coefficient values were calculated based on the recorded values of the friction torque. The results of the friction and wear studies employing the simulator confirm that the mutual angle alignment setting of the head and the cup has an impact on the value of the frictional resistance occurring in the tribological pair.