Effect of Arm Position on Width of the Subacromial Space of Upper String Musicians

Musicians often end their musical career due to musculoskeletal injury. A leading source of shoulder pain in upper string musicians is rotator cuff disease (RCD). Multiple factors contribute to its development. Compressive overload of the soft tissues of the subacromial space resulting from a decrease in the width of the subacromial space has been identified as an extrinsic factor contributing to RCD development. The purpose of this study was to characterize the width of the subacromial space by measuring acromial-humeral distance (AHD) of upper string musicians, while their arms are in standard playing positions.

Experienced musicians (n=23) were recruited from local communities. Shoulder ultrasound images were collected using standard imaging techniques. Images were collected and the AHD measured while the musician's arm was in positions associated with playing the violin.

On the right side, the arm position main effect was significant (p<0.001): the AHD in the 4th string position (8.8±1.9 mm) was less than the 1st string (11.3±1.4 mm) and resting (11.7±1.3 mm) positions. There was no difference in AHD between resting (10.0±5.8 mm) and instrument-support positions (10.6±1.5 mm). The resting AHD was smaller (p=0.04) on the right side compared to the left (12.2±1.4 mm). There was not statistically significant difference (p=0.138) in the occupation ratio (supraspinatus tendon thickness/AHD) between the right (mean 0.543±0.80 mm) and left sides (mean 0.510±0.087 mm).

The AHD measurement decreased in the playing positions compared to resting positions. Treatment interventions that help musicians maximize the width of their subacromial space might help reduce the prevalence of shoulder pain in this population.