Hook plate fixation is a treatment method for the displaced distal clavicle fracture with favorable results regarding bone union and shoulder function, however possible complications include impingement syndromes, subacrormial erosions, acromial fractures, and periprosthetic fractures. In this report, we observed 3 cases of periprosthetic fracture after hook plate fixation. All cases of periprosthetic fractures were initiated at the medial end screw holes. The causes of these periprosthetic fractures appeared to be the off centered fixation of medial end screws near the anterior or posterior cortex which were specific during operations with hook plates with more than 6 holes and the increased stress on the medial end screw by over-reduced or inferiorly reduced position of the distal end of the clavicle by the hook plate.