Adaptive patterns of movement during arm elevation test in patients with shoulder impingement syndrome.

The purpose of this study was to determine if a distinctive characteristic exists in the pattern of movement (scapular elevation and upward rotation to reduce impingement) and associated muscular activities during arm elevation in subjects with shoulder impingement (SI) that is associated with the severity of the disease. Fourteen subjects (7 amateur athletes and 7 student athletes) with SI and 7 controls performed arm elevation in the scapular plane. Scapular kinematics (upward rotation, elevation, tipping, and scapulohumeral rhythm) and muscular activity [upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and deltoid] were measured by an electromagnetic motion tracking system and surface electromyography, respectively. Subjects with SI had greater elevation of the scapula (11.9 mm, p < 0.005) and less peak scapular posterior tipping (10.6°, p < 0.02) than controls. In more severe subjects (amateur athletes), the elevation and posterior tipping of the scapula were correlated with an increase in the UT (R = -0.818, p = 0.025) and a decrease in SA (R = 0.772, p = 0.040) activity, respectively. Our results identified a characteristic compensatory scapular elevation to reduce impingement during arm elevation in subjects with SI. Assessing scapular elevation during arm elevation may be a useful functional marker for evaluating impingement status and associated muscle function. Additionally, SA and LT muscle strengthening may improve SI.

RT3 accelerometer shoulder activity: discrimination of activity levels by the RT3 accelerometer for the assessment of shoulder physical activity (SPA).

We investigated whether the RT3 accelerometer can be used to discriminate and characterize the different levels of shoulder physical activity (SPA) in both patients and healthy adults. Twenty healthy adults and 20 patients with shoulder disorders (SDs) performed activities at 5 levels of difficulty (easy, easy-moderate, moderate, hard-moderate, hard) with the same RT3 accelerometer fixed on the arm. The Vector Magnitude (VM) is the square root of the sum of squares from each axis to determine the overall magnitude of activity. The SPA counts of healthy group were significantly higher than the patient group in every level except easy (31-38 VM counts difference, p < 0.01). For both groups, the hard task demonstrated higher counts as compared to the other tasks. The easy task showed lower counts as compared to the other tasks. In the patient group, significant correlation between FLEX-SF scores and counts from the RT3 (R = -0.72, p < 0.05) was found in the moderate tasks. The results of this study showed that RT3 can be a potential measurement tool to (1) characterize the difference of SPA between two groups; and (2) partially discriminate the different levels of SPA. The correlations between self-reported function scores and SPA RT3 counts are dependent on self-reported task difficulty.