ABSTRACT: AIM:To investigate the effectiveness of ultrasound-guided release of the first annular pulley and compare results with the conventional open operative technique. METHODS:In this prospective randomized, single-center, clinical study, 32 patients with trigger finger or trigger thumb, grade II-IV according to Green classification system, were recruited. Two groups were formed; Group A (16 patients) was treated with an ultrasound-guided percutaneous release of the affected A1 pulley under local anesthesia. Group B (16 patients) underwent an open surgical release of the A1 pulley, through a 10-15 mm incision. Patients were assessed pre- and postoperatively (follow-up: 2, 4 and 12 wk) by physicians blinded to the procedures. Treatment of triggering (primary variable of interest) was expressed as the "success rate" per digit. The time for taking postoperative pain killers, range of motion recovery, QuickDASH test scores (Greek version), return to normal activities (including work), complications and cosmetic results were assessed. RESULTS:The success rate in group A was 93.75% (15/16) and in group B 100% (16/16). Mean times in group A patients were 3.5 d for taking pain killers, 4.1 d for returning to normal activities, and 7.2 and 3.9 d for complete extension and flexion recovery, respectively. Mean QuickDASH scores in group A were 45.5 preoperatively and, 7.5, 0.5 and 0 after 2, 4, and 12 wk postoperatively. Mean times in group B patients were 2.9 d for taking pain killers, 17.8 d for returning to normal activities, and 5.6 and 3 d for complete extension and flexion recovery. Mean QuickDASH scores in group B were 43.2 preoperatively and, 8.2, 1.3 and 0 after 2, 4, and 12 wk postoperatively. The cosmetic results found excellent or good in 87.5% (14/16) of group A patients, while in 56.25% (9/16) of group B patients were evaluated as fair or poor. CONCLUSION:Treatment of the trigger finger using ultrasonography resulted in fewer absence of work days, and better cosmetic results, in comparison with the open surgery technique. It is a promising method that represents excellent results without major complications, so that it could be possibly be established as a first-line treatment in the trigger finger's disease.