The effect of simulated scapular winging on glenohumeral joint translations Andreas M. Mueller, MD a,b , Vahid Entezari, MD a , Claudio Rosso, MD a,b , Brett McKenzie, BS a , Andrew Hasebrock a , Andrea Cereatti, PhD c , Ugo Della Croce, PhD c , Joseph P. DeAngelis, MD d , Ara Nazarian, PhD a, *, Arun J. Ramappa, MD d a Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA b Orthopaedic Department, University Hospital Basel, Basel, Switzerland c Department of Biomedical Sciences, University of Sassari Medical School, Sassari, Italy d Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, USA Hypothesis: In this study, we aim to test whether scapular winging results in a significant change in gle- nohumeral translation in the initial phase of the throwing motion. Methods: Six shoulders underwent an abbreviated throwing motion (ATM) from late cocking to the end of acceleration by use of a validated robotic system. The intact specimens were tested to establish a baseline. The position of the scapula was then affected to simulate scapular winging by placing a cylindrical wedge under the inferior angle of the scapula, and the ATM was performed again. For both conditions, the average glenohumeral translations and scapular rotations were plotted over time to calculate the area under the curve, as a representative of the overall glenohumeral translations and scapular rotations observed during the ATM. Results: Throughout the motion, the winged scapulae showed, on average, 7.7  more upward rotation, 1.6  more internal rotation, and 5.3  more anterior tipping as compared with the baseline. The scapular position relative to the hanging arm was significantly different between the baseline and scapular winging conditions in all arm positions, except for maximal external rotation and the neutral position. Comparing the area under the curve at baseline and with scapular winging indicated that scapular winging significantly increased anterior translation of the glenohumeral joint whereas translation in the superior/inferior and medial/lateral directions did not result in a change in translation. Discussion: These results may suggest a more important role of abnormalities in scapular position in predisposing throwing athletes to shoulder injuries of the anterior capsulolabral structures and consecutive glenohumeral instability. Level of evidence: Basic Science Study, Biomechanics. Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Shoulder; scapula; winging; dyskinesia; joint motion; translation Scapular dyskinesia is believed to be a common cause of shoulder pain and dysfunction in the overhead athlete. 3,4,9 Imbalances in the periscapular stabilizers No institutional review board approval was required for this study. *Reprint requests: Ara Nazarian, PhD, Center for Advanced Ortho- paedic Studies, 330 Brookline Ave, RN115, Boston, MA 02215, USA. E-mail address: anazaria@bidmc.harvard.edu (A. Nazarian). J Shoulder Elbow Surg (2013) -, 1-7 www.elsevier.com/locate/ymse 1058-2746/$ - see front matter Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2012.09.010