Mast cell presence in tendon sheaths of trigger fingers: implications on pathogenesis and clinical presentation.

Trigger finger is a common hand disorder; however, its pathogenesis remains unknown. In this study, we aimed to investigate mast cells, fibroblast activators that synthesize collagen, in the tendon sheaths of trigger fingers. We investigated the presence of mast cells and their association with changes in the collagen content of the tendon sheath and clinical data. We performed a multicenter prospective study of 77 adult patients with trigger finger who had undergone resection of the first annular pulley between August 2012 and January 2020. The tendon sheath was immunostained with an anti-tryptase antibody to confirm mast cell presence. The percentage of collagen in the tendon sheath was determined by picrosirius red staining observed through a polarization microscope. The clinical data, including the duration from symptom onset to surgery, severity, pain numerical rating scale, and Hand20 scores, were evaluated. Tryptase-positive mast cells were recognized in 83.5% of all specimens. The mast cell presence group (Group P) had a significantly higher percentage of type-3 collagen in the tendon sheath than the non-mast cell presence group (Group N) (Group P, 15.6%; Group N, 12.7%;  = 0.03). Moreover, Group P had significantly higher pain numerical rating scale (Group P; 5, Group N; 3,  = 0.04) and Hand20 (Group P; 35.5, Group N; 13.0,  = 0.01) scores than Group N. These findings suggest that mast cell presence in the tendon sheath of the trigger finger is related to the pathology and clinical symptoms of trigger finger.