Change in the CCD angle and the femoral anteversion angle by hip prosthesis implantation]

PURPOSE: The aim of the present study was to measure and interpret the change of the collodiaphyseal (CCD) angle and femoral anteversion after total hip replacement. METHODS: We prospectively examined 52 patients with coxarthrosis, who were treated by total hip replacement. Preoperatively and postoperatively we used a standard X-ray ap view to measure the CCD angle and computerized tomography to determine the femoral anteversion. These projected angles were converted into the real angles by using the method of K?nig and Schult. RESULTS: On average the preoperative real CCD angle was 128 degrees (+/- 8.9 degrees) and the postoperative angle 145 degrees (+/- 4.8 degrees), preoperatively the real femoral anteversion angle was 14.1 degrees (+/- 6.9 degrees) and postoperatively 10.8 degrees (+/- 6.2 degrees). CONCLUSIONS: The effect of the postoperative valgisation can be explained by the given CCD angle of the used femoral stem prosthesis of 140 degrees (cemented Weller II stem) and 145 degrees (cementless CLS classic stem). It is possible that due to the valgisation and the decreased offset of the femoral stem prosthesis compared to the preoperative conditions the gluteal muscles are insufficient and overloaded. It is also known that the change of the femoral anteversion from the physiological conditions causes an increase of the torsional moment. The resulting increased interface load could possibly be a reason for loosening of the femoral stem. The conclusion can be drawn that the CCD angle and the femoral anteversion should more carefully be considered by the surgeon in total hip replacement. This could be reached by an exact implantation technique and the choice of the appropriate stem prosthesis with different CCD angles.