Etiology and surgical treatment of pediatric trigger finger: Quantitative measurements of the cross-sectional configuration of the flexor tendon using ultrasonography

Abstract Background: This study quantitively evaluated the cross-sectional area of the flexor tendon and the area under the A1 pulley using ultrasonography in patients with unilateral pediatric trigger finger (PTF). The surgical outcome following release of the A1 pulley together with the proximal one-third of the A2 pulley was determined.Methods: We enrolled 32 trigger fingers of 29 patients diagnosed with unilateral PTF. The cross-sectional configuration of the flexor tendon was determined in 12 trigger fingers of 10 patients using ultrasonography. The ultrasonography measurements consisted of the anteroposterior (AP) diameter, radioulnar (RU) diameter, cross-sectional area of the flexor tendon at the level of the greatest AP diameter of the flexor tendon proximal to the A1 pulley, and the inner dimensions of the A1 pulley. The measurements were repeated on the contralateral normal same finger. The efficacy of the surgical release of the A1 pulley together with that of the proximal one-third of the A2 pulley was assessed in 11 trigger fingers of 11 patients who underwent surgical intervention for PTF.Results: The average RU measurement and cross-sectional area of the flexor tendon were larger than the inner dimensions of the A1 pulley in PTF patients. The average AP, RU, and cross-sectional area measurements in the area under the A1 pulley were significantly larger in the trigger finger than in the contralateral normal finger (P < 0.05). The average RU and cross-sectional area measurements of the flexor tendon proximal to the A1 pulley were also significantly larger in the trigger finger than in the contralateral normal finger (P < 0.05). In 10 of the 11 (91%) surgically treated fingers, successful resolution of triggering without recurrence was achieved after release of the A1 pulley together with the proximal one-third of the A2 pulley. One finger had recurrent triggering, which was successfully treated with complete A2 pulley and partial A3 pulley release. The patient remained asymptomatic after the revision procedure. No other complications were observed. All patients were satisfied with the surgical outcomes and at the most recent follow-up evaluation had returned to full activities.Conclusions: Ultrasonographic measurements in PTF patients suggested that PTF is caused by a size mismatch between the flexor tendon and the area under the A1 pulley. The difference is the result of nodule formation or thickening within one or both of the flexor digitorum superficialis slips. Surgical release of the A1 pulley and of the proximal one-third of the A2 pulley is a very efficient treatment for PTF, yielding satisfactory outcomes that may shorten the duration of symptoms.