Error analysis of femoral anteversion because of malpositioning in computed tomography - Introduction of a method for positional correction

Objective: To quantify the influence of patient positioning on the determin ation of collodiaphyseal (CCD) angle and femoral neck anteversion based on computed tomography. Description of a method for positional correction. Met hods: We evaluated the CT scans of 84 femora from 77 patients, who received individually adapted prostheses. Projected as well as real anteversion and CCD angles were determined and corrected for positioning errors using a ne wly proposed mathematical method, and compared to other evaluation methods. Results and Conclusions: We determined an average tilt of 4.2 degrees in t he sagittal and of 9 degrees in the coronary plane, which correlated defini tely with the deviations found in the graphical determination of the projec ted anteversion angle. This produced measurement errors of the projected an teversion angle of up to 10 degrees. Mathematically independent angles, suc h as projected anteversion and real CCD angle, showed only a weak correlati on. This indicates also an anatomical independence of these angles.