Femoral and tibial torsion measurements based on EOS imaging compared to 3D CT reconstruction measurements.

BACKGROUND: The EOS imaging system is an advanced piece of equipment for full-body imaging, but its reliability and reproducibility should be further verified.

METHODS: A prospective study was conducted including 18 adult volunteers (36 lower extremities) (24±2 years old). Femoral and tibial torsion were measured by both EOS imaging and three-dimensional computed tomography (3D CT) reconstruction. Bland-Altman plots were performed to evaluate the difference between femoral and tibial torsion measurements obtained by these two methods. The intraclass correlation coefficient (ICC) was used to evaluate intrareader agreement.

RESULTS: The mean difference between the two methods was 3° (range, -9° to 4°) for femoral torsion, 0° (range, -6° to 6°) for tibial torsion and 0° (range, -4° to 5°) for femorotibial torsion. No statistically significant difference between the measurements of the two methods was detected by Bland-Altman plots. With the exception of one measurement of femoral torsion, one measurement of tibial torsion and one measurement of femorotibial torsion, all EOS imaging measurements were within the 95% limits of agreement (the mean ± 1.96 SD). Intrareader agreement was statistically significant (P<0.001) for all measurements, with high ICCs. For EOS imaging, the ICC was 0.92 for the femoral measurement, 0.92 for the tibial measurement and 0.918 for the femorotibial measurement; the corresponding values for CT were 0.950, 0.927 and 0.889.

CONCLUSIONS: There was good agreement between EOS imaging based and 3D CT reconstruction based technique in measuring femoral, tibial and femorotibial torsion; and good reliability and reproducibility of EOS Imaging in measuring femoral, tibial and femorotibial torsion was also verified.