In trauma settings, including the management of outcomes, there is no consensus on the most appropriate reconstructive method in the presence of severe bone loss of the proximal humerus. The objective of this report is to evaluate the short-term functional outcomes of two patients in whom reverse shoulder megaprosthesis was used to treat the failure of trauma surgery with severe bone loss. The secondary objective was to compare the results obtained with the literature regarding the use of megaprosthesis in shoulder trauma surgery. The patients showed a satisfying functional recovery and increased quality of life. At the 12-month follow-up, no complications occurred. Regarding the risk of complications, especially the risks of mobilization of the megaprosthesis, the CT-based intraoperative navigation system optimizes the configuration of the screw for the initial fixation of the glenoid component. Shoulder megaprosthesis appears to be a viable option not only in oncologic surgery but also in cases of failed trauma surgery. The functional results, considering functional score and range of motion, are encouraging and allow patients to improve their quality of life.