We evaluated the long-term clinical results of acute complete acromioclavicular dislocations treated by reconstruction of the acromioclavicular and coracoclavicular ligament using trapezius muscle fascia. Open reduction and internal fixation was performed using the clavicular hook plate in 12 patients with acute complete acromioclavicular joint dislocation, and the acromioclavicular and coracoclavicular ligaments were reconstructed using trapezius muscle fascia. Radiographic evaluations were conducted postoperatively. We evaluated the functional results with constant scoring system and radiological results at the final follow-up visit. The mean Constant score at the final follow-up visit was 91.67 (range, 81 to 100). The results were excellent in eight patients (66.7%) and good in four patients (33.3%). Three patients with scores from 80 to 90 had mild pain during activity, but this did not affect the range of motion of the shoulder. All patients have returned to their preoperative work without any limitations. Compared with the contralateral side, radiography showed anatomical reposition in the vertical plane in all cases. The hook-plate fixation with ligament reconstruction was successful in treating AC dislocations. The acromioclavicular and coracoclavicular ligament were reconstructed by trapezius muscle fascia that keep the distal clavicle stable both vertically and horizontally after type III injuries.