An ultrasonographic analysis of the structures of the subacromial space, as they relate to the postures of upper string musicians

Background: The leading source of general population shoulder pain is subacromial impingement syndrome (SAIS) which can contribute to rotator cuff disease (RCD). It has been reported that up to 12% of musicians end their musical career due to musculoskeletal injury. SAIS is a common source of shoulder pain in bowing arm of upper string musicians. However, the mechanisms leading to shoulder pain, in upper string musicians, are not well known.;Purpose: The purpose of this study was to characterize aspects, of the subacromial space anatomy, while in standard playing positions of upper string musicians. Specifically measurements taken of the acromiohumeral distance (AHD) and supraspinatus tendon thickness.;Methods: Experienced musicians (n = 23) were recruited from the university and local communities. Ultrasound images of the participant's shoulders were collected using standard imaging techniques.;Results: On the right side, the arm position main effect was significant (p < 0.001), the AHD in the 4th string position (8.459 +/- 0.449mm) was less than the 1st string (10.978 +/- 0.319mm) and resting (11.713 +/- 0.327mm) positions. There was a significant difference in the AHD between the resting (13.428 +/- 0.606mm) and the 1st finger, 1st string (10.765 +/- 0.488mm) positions in the left side. The resting AHD was smaller (p < 0.001) on the right side (11.713 + 0.327mm) compared to the left (12.273 +/- 0.404mm). Tendon thickness of the left shoulder (5.687 +/- 0.211mm) was not significantly different when compared to the right side. (5.889 +/- 0.262mm). There was a statistically significant difference (p < 0.001) in the occupation ratio (tendon thickness / AHD) between the left (0.472 +/- 0.021mm) and right shoulder (0.507 +/- 0.022mm).;Conclusions and Practical Relevance: The reduced resting AHD measurements of the right shoulder and the reduction of AHD measurements as the arm is brought into elevation, suggest upper string musicians are at greater risk for RCD than the general population, especially on the right side. Treatment interventions that help musicians maximize the width of the subacromial space may reduce the prevalence of shoulder pain in this population.