[Quantification of position-related errors in measurement of antetorsion of the femur with computerized tomography--introduction of a method for positional correction].
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.


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.
Müller
O
O
Orthopädische Klinik und Poliklinik, Universität Tübingen. otto.mueller@med.uni-tuebingen.de
Martini
F
F
Haller
M
M
Schaich
M
M
Sell
S
S
D000328:Adult; D000368:Aged; D017760:Bone Malalignment / Q000000981:diagnostic imaging* / Q000601:surgery; D005260:Female; D006617:Hip Dislocation / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008432:Mathematical Computing; D008875:Middle Aged; D010027:Osteotomy; D012016:Reference Values; D014057:Tomography, X-Ray Computed / Q000379:methods*