Objective: To quantify the influence of patient positioning on the determination of collodiaphyseal (CCD) angle and femoral neck anteversion based on computed tomography. Description of a method for positional correction.
Methods: 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 newly proposed mathematical method, and compared to other evaluation methods.
Results and conclusions: We determined an average tilt of 4.2 degrees in the sagittal and of 9 degrees in the coronary plane, which correlated definitely with the deviations found in the graphical determination of the projected anteversion angle. This produced measurement errors of the projected anteversion angle of up to 10 degrees. Mathematically independent angles, such as projected anteversion and real CCD angle, showed only a weak correlation. This indicates also an anatomical independence of these angles.