Snapping of the Subacromial Bursa: A New Cause of Shoulder Pain Demonstrated with Dynamic Ultrasound

Introduction. Compared to pain, weakness, and stiffness, snapping phenomena are less frequently reported. The anatomical implication of subacromial bursa on snapping syndrome has not yet been studied despite of the fact that subacromial volume is implicated in this syndrome. The aim of this study is to analyze the anatomical and dynamic implication of the subacromial bursa in snapping syndrome. Methods. We conducted a retrospective of symptomatic case series (n = 9) study including dynamic sonography, video recordings resulting from standardized clinical dynamic examinations, and the results of shoulder magnetic resonance imaging. Nine patients complaining of snapping phenomena of the anterior shoulder (seven males and two females, mean age: 37.1 ± 10.2 years old), in whom dynamic sonography could confirm the diagnosis of snapping subacromial bursa, were included in this study. Results. All the patients included in this study presented non-traumatic painful snapping syndrome without plication before the snap on the dynamic sonography. All complained of a disabling snap of the shoulder associated with pain and without folding before the snapping phenomenon. Four of them had a bursitis of the subacromial bursa diagnosed on their shoulder's magnetic resonance imagery. No significant statistical correlation (rS = -0.372; p = 0.595) was found between the triggering mechanisms, such as the snap shoulder release position, and the position of the anterior recess of the subacromial bursa relative to the biceps' tendon. Conclusions. This study highlights the anterior recess of the subacromial bursa as a previously underexplored anatomical contributor to snapping syndrome, particularly in young, physically active individuals, emphasizing the need for dynamic sonography in diagnosing this condition. The anterior recess of the subacromial bursa represents an additional cause of snapping, which especially takes place in young and physically active patients. More than sport practice, professional activities that require repetitive tasks of the shoulder seem to represent a risk factor.