Background: We evaluated trigger fingers ultrasonographically and clarified differences between fingers with and without continuous locking or snapping symptoms according to the thicknesses of the A1 pulley, flexor tendon and volar plate.
Methods: We evaluated 26 trigger fingers, divided into two groups: Group 1, 14 fingers with locking or snapping; and Group 2, 12 fingers without such symptoms. We also evaluated 26 contralateral fingers as controls (Control 1 and 2 groups). We compared each group to the respective control group according to thickness of the A1 pulley and volar plate, and cross-sectional area of the flexor tendon. In addition, nine fingers with locking or snapping and treated using corticosteroid injection were evaluated according to symptoms and sonographic findings 3-4 weeks after treatment.
Results: Thickness of the A1 pulley and cross-sectional area of the flexor tendon were greater in both Groups 1 and 2 than in controls. Thickness of the volar plate was greater in Group 1 than in Control 1, although no significant difference was seen between Group 2 and Control 2. In Group 1, eight of the nine fingers showed an alleviation of locking or snapping symptoms with corticosteroid injection, and sonographic findings showed that thickness of the volar plate was significantly decreased with corticosteroid injection, in addition to reduced thickness of the A1 pulley.
Conclusion: In addition to thickening of the A1 pulley, thickening of the volar plate may represent an important contributor to continuous snapping or locking symptoms.