In Vivo Evaluation of Subacromial and Internal Impingement Risk in Asymptomatic Individuals

OBJECTIVEThe study aim was to evaluate subacromial and internal impingement risk between shoulders (dominant/non-dominant) during dynamic motion using subject-specific anatomy and precise in vivo kinematics. DESIGNIn a prospective cross-sectional study, 9 subjects underwent bilateral MR (N=18 shoulders) and fluoroscopic imaging during external rotation at 90° abduction (ER) and elevation. Subject-specific bone models were created and distances from footprint to (a) acromion and (b) glenoid were measured to evaluate risk. RESULTSThroughout elevation, subacromial impingement risk was greater in the dominant shoulder (P=0.0178). Regardless of side, high subacromial impingement risk occurred at 30% (78°), 50% (101°), and 70% (57°) of the elevation cycle (P