Fluoroscopic assessment of rotator cuff fatigue on glenohumeral arthrokinematics in shoulder impingement syndrome

BackgroundAlthough prior researchers have assessed glenohumeral arthrokinematics using isometrically held arm postures with standard radiographs, dynamic assessment of glenohumeral arthrokinematics has been limited. This study utilized video fluoroscopy to analyze superior inferior glenohumeral migration during dynamic arm elevation in individuals with outlet impingement syndrome, before and after fatigue of the rotator cuff.HypothesisPrior to the study, it was hypothesized that during the pre-fatigue state, glenohumeral migration would be in the superior direction, and that post-fatigue there would be a significant increase in superior migration.Materials and methodsDigital fluoroscopic videos (30 Hz) were used to analyze 20 male volunteers (27.7 ± 7.3 years) with right shoulder outlet impingement syndrome during concentric elevation of the arm in the plane of the scapula, both before and after fatigue of the rotator cuff.ResultsDuring concentric arm elevation, there was superior glenohumeral migration (1.6 mm) between 45° and 90° of arm elevation, regardless of fatigue-state (P = .02). After rotator cuff fatigue, the humeral head was positioned more superiorly on the glenoid fossa (P = .03). The position of the humeral head was 0.4 mm more superior than that reported in a previous study on healthy individuals.ConclusionThese results support prior findings that suggest superior glenohumeral migration during arm elevation is influenced both by shoulder pathology and the state of fatigue of the rotator cuff musculature. Future research should examine the effects of physical therapy and surgical interventions on glenohumeral arthrokinematics to better determine the most effective treatment methods for outlet impingement.Level of evidenceControlled laboratory study