| While evidence has been presented indicating that scapulohumeral rhythm (SHR) is altered in patients with full thickness rotator cuff tears, the role that pain plays in altering these kinematic patterns is unknown. The purpose of this study was to test the hypothesis that movement of the scapula and humerus is altered in patients with full thickness rotator cuff tears (RCT) due to pain.; Pain and shoulder kinematic data was collected on sixteen patients with symptomatic, diagnosed full-thickness rotator cuff tears, ages 40-72 years (60.2+/-8.9 years; 1.72+/-0.10 meters; 85.43+/-18.32 kg; 10 male, 6 female). Pain and function were assessed using the ASES Shoulder Assessment questionnaire. Three-dimensional kinematic data was collected using the MotionStar electromagnetic tracking system (Ascension Technology, Burlington, VT). Sensors were attached to the subject's sternum, scapula, humerus and forearm of the involved shoulder. Subjects performed humeral elevation and lowering three times in the sagittal, scapular and frontal planes, in a randomized order. After the initial testing, the subjects received a subacromial lidocaine injection to eliminate pain. Following the injection and a brief rest period (15 minutes), subjects repeated the movement and data collection protocol. Using an anatomic coordinate system and Euler angles sequences, approved by the International Society for Biomechanics, scapulothoracic and glenohumeral elevation angles along with SHR (scapulothoracic/glenohumeral) were calculated.; Paired t-tests revealed declines in SHR for humeral elevation (t(14) = 1.927, p = 0.037) and lowering (t(14) = 1.999, p = 0.033) in the frontal plane. Similar trends were also noted scapular plane elevation. Significant increases were also identified for glenohumeral elevation (t(14) = -2.057, p = 0.030) and lowering (t(14) = 2.444, p = 0.014) in the frontal plane. Significant differences were also noted between pre-injection and post-injection humeral elevation and lowering velocities.; The removal of pain resulted in a relative decrease in scapulothoracic and an increase in glenohumeral joint contributions to humeral elevation and increased humeral elevation velocities. These findings provide evidence of compensatory shifts in scapulothoracic and glenohumeral joint contributions to humeral elevation and altered humeral elevation velocities due to pain associated with RCT. |
