Purpose
The biplanar whole body imaging system (EOS) is a new tool for measuring whole body sagittal alignment in a limited space. This tool may affect the sagittal balance of patients compared to conventional whole spine radiography (WSX). This study is to investigate the difference in sagittal alignment between WSX and EOS.
Materials and Methods
We compared spinal and pelvic sagittal parameters in 80 patients who underwent EOS and WSX within one month between July 2018 and September 2019.The patients were divided based on sagittally balanced and imbalanced groups according to pelvic tilt (PT) >20˚, pelvic incidence-lumbar lordosis >10°, C7-sagittal vertical axis (SVA) > 50 mm in WSX.
Results
In sagitally imbalanced group, for WSX versus EOS, the pelvic parameters demonstrated compensation in EOS with smaller PT (27.4±11.6° vs. 24.9±10.9°, p=0.003), greater sacral slope (SS), and patients tended to stand more upright with smaller C7-SVA (58.4±17 mm vs. 48.9±57.3 mm, p=0.003), T1-pelvic angle (TPA), T5-T12, and T2-T12. However, in sagitally balanced group, these differences were less pronounced only with smaller PT (10.8±6.9° vs. 9.4±4.7°, p=0.04), TPA and T2-T12 angle, but SS and C7-SVA were similar (p>0.05).
Conclusions
EOS shows a negative SVA shift and lesser pelvic tilt than WSX especially in patients with sagittal imbalance. When making a surgical plan, surgeon should consider these differences between EOS and WSX.