Radiologische Rotationsfehlerbestimmung am Femur - Computertomographie, optimierte Meßgenauigkeit und Expositionsdosis

Abstract

58 Patients, suspicious to have rotation deformity of the femur, were examined. To compare the value of diagnostic methods in measuring the degree of malrotation we estimated this degree using clinical examination and calculated the anteversion of the femoral neck, taking radiographs in the technique of Dunn and Rippstein, and a modified method of computed tomography. Only in twelve cases the direction of malrotation was corresponding in all three methods, although considerable variations in quantitative results were noted. Maintaining the exact position of the patient, necessary to get reproducible results using conventional X-ray technique, was impossible in most cases of patients with posttraumatic joint-stiffness and malalignment. Determination of femoral neck anteversion using this modified method of CT is a quick, reproducible technique to calculate the degree of malrotation, insensitive to the position of the patient. By means of this CT method it was possible to approach the highest accuracy in precise preoperative planing. Furthermore the radiation exposure could be reduced in a range of 20%-40%.

Femoral anteversion: significance and measurement

“…Alternatively, two axial slices can be taken to define the femoral neck axis, one at the femoral head and the other at different heights of the distal femoral neck (Egund and Palmer, 1984;Murphy et al, 1987;Waidelich et al, 1992;Buddenbrock et al, 1997). Where scans are not aligned with the femoral shaft axis, calculation may be needed to transform the torsion to a reference plane, as positioning-related measurement errors can be as large as 8.8° (Hermann and Egund, 1997).…”

“…However, the height (Jend, 1986; Sugano et al, 1998a) and angle of slices used for the 3D reconstruction (Tomczak et al, 1997; Schneider et al, 1997; Beebe et al, 2017) affect the final result, as the femoral neck has an asymmetrical shape (Backman, 1957). Alternatively, two axial slices can be taken to define the femoral neck axis, one at the femoral head and the other at different heights of the distal femoral neck (Egund and Palmer, 1984; Murphy et al, 1987; Waidelich et al, 1992; Buddenbrock et al, 1997). Where scans are not aligned with the femoral shaft axis, calculation may be needed to transform the torsion to a reference plane, as positioning‐related measurement errors can be as large as 8.8° (Hermann and Egund, 1997).…”

Subtrochanteric osteotomy for femoral mal-torsion through a surgical dislocation approach

“…Torsional components may contribute to intra-articular and extra-articular impingement [ 12 ], as well as instability [ 13 ] and tendency to traumatic posterior dislocation [ 14 , 15 ]. Improvements in advanced cross-sectional diagnostic imaging, such as standardized protocols for computed tomography (CT) [ 16 ] and magnetic resonance imaging [ 8 , 17 ], have proven useful adjuncts to clinical examination for more accurate measurement of rotational anatomy.…”

Diagnosis of posttraumatic leg deformities

“…Aufgrund der besseren Reproduzierbarkeit setzte sich der sonograAbb. 10 Die sonographische Messung der Tibiatorsion wurde erstmals von Joseph et al [39] 1987 publiziert. Als Referenzlinien zur Torsionswinkelmessung dienen an der proximalen und distalen Tibia die gelenkflächennahen posterioren Knochenkonturen.…”

“…Die Strahlenbelastung ist bei einem Übersichtsscan ("scout view") zur Län-genbestimmung deutlich geringer als bei der Ganzbeinaufnahme. Die Computertomographie ist deshalb heute aufgrund der großen Genauigkeit und der geringeren Strahlenbelastung der Goldstandard zur Bestimmung der relativen Beinlängen [10,19,90].…”