Sagittal balance measures are more reproducible when measured in 3D vs in 2D using full-body EOS® images

An innovative low-dose X-ray biplanar imager (EOS®) allows measurement of the whole-body in standing-position which is necessary for the evaluation of spinal deformities. A total of 60 asymptomatic subjects (ages 20–81 years) were evaluated using the 3D workflow called postural assessment and 2D measures. Subjects were measured twice each by two new observers following training, including: lordosis/kyphosis, pelvic parameters, sagittal-vertical axis, and spinal-sacral angle. Intra- and inter-observer reproducibility and similarity were compared between 2D and 3D measures. The intraclass correlation coefficient (ICC) was very high for the 3D measures (>0.9) and excellent for the 2D measures (>0.75). In all cases, the overall mean absolute difference between repeated 3D measures was less than 2°, or 2 mm. For all parameters, the inter- and intra-observer reproducibility in 3D measures were significantly superior to 2D measures (p < 0.03). This study demonstrated that 3D measures have better reproducibility than 2D for sagittal balance. • Reproducibility of sagittal balance 2D/3D measurements was evaluated using EOS® full-body radiographs. • Inter- and intra-observer reproducibility were significantly superior for 3D measures vs. 2D. • 3D measures have better reproducibility than 2D for sagittal balance.