The changes in morphology and stiffness of supraspinatus in volleyball players with subacromial impingement syndrome

To compare the morphology and stiffness of supraspinatus between adolescent volleyball players with and without SAIS. To compare the morphology and stiffness of supraspinatus between adolescent volleyball players with and without SAIS.

Seven high-school volleyball players with SAIS (SAIS group) and another seven asymptomatic players (control group) from the same team were recruited. All the participants received the sonography and elastography examinations for measuring acromiohumeral distance (AHD), thickness (TH_M and TH_T), and strain ratio (SR_M and SR_T) of supraspinatus muscle and tendon. Mann-Whitney U test was used to examine the difference between groups. 

Both the SR_M (1.06 ± 0.17 v.s. 0.79 ± 0.07, p= 0.009) and SR_T (1.33 ± 0.84 v.s. 0.78 ± 0.11, p = 0.048) in the SAIS group were significantly higher than that in the control group. However, the two groups had no significant difference in AHD, TH_M, and TH_T. In addition, the ratio of TH_T to AHD did not differ.

The changes in supraspinatus properties may be the primary factor of SAIS in adolescent volleyball players, although there was no change in tendon thickness. Similar AHD and ratio of TH_T to AHD between both groups may imply that the subacromial space was not altered. All measurements were conducted in static status instead of arm elevation, which may limit the generalization to dynamic situations.

In addition to the neuromuscular control of the scapula, musculotendinous properties of supraspinatus need to be monitored to prevent rotator cuff-related disorders in overhead athletes. Future studies may be considered to evaluate the intervention effects on supraspinatus stiffness in volleyball players.