124 - A Comparison of Cobb Angle Measurements According the Two Standardized Imaging Modalities Used for Scoliosis Diagnostic: 2D Radiography Versus 3D EOS Stereoradiography.

Introduction: EOS stereoradiographs and 2D X-rays imaging modalities are widely used to assess and diagnose scoliosis from patients. EOS stereoradiography is a 3D imaging technique which uses less radiation dose than 2D X-rays acquisition and allows a complete 3D analysis of the full-spine in a single-acquisition. Despite its efficacy to analyze sagittal and coronal spinal parameters, the EOS machine is not available in all surgical spine centers and some of them continue to assess scoliosis using traditional and standardized2D X-rays acquisitions. Even if EOS stereoradiography is assumed to be more efficient than 2D X-rays acquisitions in terms of resolution, accuracy, and radiation dose exposure, there is no data comparing those two imaging modalities when measuring Cobbangles.
Aims/

Objectives: Assess the difference in Cobb angle measurements from full-spine standard 2D radiographs versus 3D EOS stereoradiographs.

Methods: Data from100 non-treated adult patients with low back pains who had a full-spine standing X-rays acquisition and a 3D EOS stereoradiography were retrospectively collected from 2 different study centers. The delay between the two imaging modalities did not exceed 3 months. Cobb angles were measured twice by two independent observers on both modalities. Cobb angles obtained from 2D X-rays acquisitions were compared to those obtained on EOS stereoradiographs (comparisons applied: 2D X-ray versus 2DEOS, 2D X-ray versus 3D EOS, 2D EOS versus 3D EOS). Intraclass correlation coefficients were calculated for all of the measurements.

Results: The intraclass correlation coefficients were more than 0.85 with 95% CI between 0.72 and 0.96. The means Cobb angles were 11.1± 6.7°, 11.2 ± 7.3°, 10.7 ± 7.4° and 11.1 ± 7.8° on X-ray, EOS (2D analysis), EOS 3D (radio plane) and EOS 3D (patient plane)respectively. The means difference from Cobb angles measured on X-ray and EOS were no more than 0.5 ± 2.5° when comparing all the measuring methods (2D X-ray versus 2D EOS, 2D X-ray versus 3D EOS, 2D EOS versus 3D EOS).

Conclusions: Measuring Cobb angles on standard 2D X-rays acquisitions seems to be equivalent to those measured on EOS stereoradiographs. Both imaging modalities are then assumed to be equivalent when assessing or diagnosing scoliosis based on Cobb angle measurement.