We experienced a case of impingement caused by a bone fragment which was impacted between acromion and humeral head in a child. The bone fragment came from antero-inferior glenoid fracture. Satisfactory clinical results and stability were obtained by arthroscopic bone fragment removal. In case that bone fragment is located in the upper shoulder joint and results in impingement, We must consider not only greater tubercle fracture but also glenoid fracture. Magnetic resonance imaging can assist in the preoperative diagnosis.