Dynamic ultrasound of the subacromial-subdeltoid bursa in patients with shoulder impingement: a comparison with normal volunteers

The purpose of the study was to determine if the thickness of the subacromial-subdeltoid (SASD) bursa during dynamic ultrasound and on static views differs between patients with shoulder impingement syndrome and healthy volunteers. Twenty-two patients with a clinical diagnosis of shoulder impingement syndrome and 23 healthy volunteers were recruited. A subset of patients showing an immediate symptom response following intrabursal injection was identified as "injection responders". Ultrasound of the shoulder was performed on all participants using three standard static views and two dynamic views (before and after arm abduction). The thickness of both the intrabursal fluid and the superficial peribursal fat was measured on all views. The bursal thickness measurements in the two groups were compared using a t test for significance. The mean increase in SASD bursal fluid thickness following arm abduction was not statistically different among all patients (0.39 +/- 0.41 mm) and controls (0.35 +/- 0.32 mm), p = 0.72. The same was true comparing injection responders (0.46 +/- 0.49 mm) with controls, p = 0.41. On static views, greater bursal fluid thickness was found in patients (1.01 +/- 0.48 mm) compared with controls (0.67 +/- 0.32 mm) when using the short axis view of the supraspinatus, p = 0.006. No statistically significant difference was found between injection responders and controls when measuring peribursal fat thickness on any view. Gathering of the SASD bursa demonstrated during dynamic ultrasound does not necessarily indicate painful impingement of the bursa as it is found to a similar degree in patients with a clinical diagnosis of impingement and healthy volunteers.