Digital fluoroscopic video assessment of glenohumeral migration: Static vs. Dynamic conditions

The purpose was to compare glenohumeral (GH) migration, during dynamic shoulder elevation and statically held positions using digital fluoroscopic videos (DFV). Thirty male volunteers (25+/-4 years) without right shoulder pathology were analyzed using DFV (30Hz) during arm elevation in the scapular plane. DFV were obtained at the arm at side position, 45 degrees , 90 degrees , and 135 degrees for static and dynamic conditions. GH migration was measured as the distance from the center of the humeral head migrated superiorly or inferiorly relative to the center of the glenoid fossa. Inter-rater reliability was considered good; ICC (2,3) ranged from 0.83 to 0.92. A main effect was revealed for contraction type (p=0.031), in which post-hoc t-tests revealed that humeral head was significantly more superior on the glenoid fossa during dynamic contraction. A main effect was also revealed for arm angle (p<0.001), in which post-hoc t-tests revealed significantly more superior humeral head positioning at 45 degrees , 90 degrees , and 135 degrees when compared to arm at side (p<0.001), as well as at 90 degrees compared to 45 degrees (p=0.024). There was no interaction effect between angle and contraction type (p=0.400). Research utilizing static imaging may underestimate the amount of superior GH migration that occurs dynamically.