[The influence of surgically introduced muscle tension on the function of total hip prostheses (author's transl)].

The functional results of total hip prosthesis are influenced significantly by the tension given to the glutaeus medium muscle at operation. Low tension may result in a limp (positive Trendelenburg sign), high tension may decrease movement. In 206 cases of total hip replacement the Trendelenburg sign (grades from 0-3), the movement (in grades 0-4) and a grade of extension (distance or prosthetic femoral head and plastic acetabulum in cm at maximal extension after resection of the capsule) have been evaluated. In 191 hip joints not operated before the Trendelenburg sign was negativ before operation in only 31%, after operation it was negativ in 73%. The evaluation of the partial correlation coefficient showed a definite relation between Trendelenburg sign and the grade of extension. The higher the extensibility of the hip joint the more pronounced the Trendelenburg sign. In 71% of 191 cases the movement was increased after total hip replacement. With increased extensibility, the movement becomes better. However it is also related to the movement before operation. The optimal muscular tension and movement of the hip joint can be expected at an extension grade of 1.5-2.0 cm (distance between the prosthetic femoral head and the plastic acetabulum at maximal extension during operation).