Background <p>Scapulothoracic dyskinesis (SD) is a common functional disorder of the shoulder characterized by abnormal positioning or mobility of the scapula. Kibler’s classification describes three catagories of SD. Clinical and radiological diagnosis remain challenging, and no simple 3D assessment method is currently available.</p> Purpose <p>The objectives of this study were (1) to determine whether scapular positioning on bone models simulating SD conditions can be assessed using low-dose EOS biplanar imaging, and (2) to evaluate the inter- and intra-observer reproducibility of this method.</p> Methods <p>A full-scale scapulothoracic bone model including bilateral scapulae, thorax, and spine was used. Scapular positions were adjusted to simulate one normal condition and three SD patterns corresponding to Kibler’s classification. EOS imaging was performed in seven different positions for each model. Seven anatomical landmarks were identified on stereoradiographs to obtain 3D scapulothoracic measurements. Twenty-eight sets of EOS measurements were analyzed by two independent observers. Inter- and intra-observer reproducibility were assessed.</p> Results <p>Landmark identification and scapulothoracic measurements were feasible in all cases. Inter- and intra-observer reproducibility were &gt; 0.80 for all parameters except internal rotation (0.75). The mean difference between observers was 0.3 ± 2.8° for angular measurements and 0.1 ± 0.5&#xa0;cm for distance measurements.</p> Conclusion <p>EOS biplanar imaging enables reproducible measurement of scapulothoracic positioning on dry bone using a simplified method. These findings suggest that this approach may be a promising tool for 3D assessment of scapular positioning, although validation in clinical settings is required.</p>