Open reduction and internal fixation with a locking plate are performed frequently to treat fractures of the proximal humerus. Avascular necrosis and non-union or malunion are potential complications of this procedure, which lead to specific fracture sequelae. The aim of this study was to investigate the clinical and radiological results of patients treated by removal of a failed locking plate of the proximal humerus and simultaneous implantation of a reverse total shoulder prosthesis. Twenty-one patients (f = 17, m = 4; mean age 70 years) out of 29 patients were available for follow-up after a mean period of 45 (30-65) months. At follow-up, all patients were assessed with the constant score and the ASES score as well as plain radiographs. In comparison with the preoperative values, abduction (31° vs. 115°; p < 0.001) and forward flexion (34° vs. 121°; p < 0.001) improved until follow-up, while the pain score on a visual analog scale decreased (6.7 vs. 0.9; p < 0.001). At follow-up, the mean ASES score rated 73 and the constant score rated 62. The radiologic findings included scapular notching (n = 7; 33%), radiolucency (n = 4; 19%), heterotopic ossifications (n = 3; 14%), and stress shielding (n = 4; 19%). Reverse total shoulder arthroplasty is a useful instrument for the treatment of failed locking plate osteosynthesis of the proximal humerus in elderly patients. The patients benefit from both pain relief and improved shoulder function. The rate of radiologic changes like scapular notching, radiolucency, stress-shielding and heterotopic ossifications at follow-up is notable.