Reversed shoulder arthroplasty (RSA) is recommended in case of severe muscle deficiency, along with important joint wear. Although having a correct placement of the prosthesis after the operation and a recovery of the mobility, several cases of scapula fracture are reported, in the region of the scapular spine or the acromion. Complication occurs 3 to 6 months after the surgery and may necessitate a second intervention. Such fractures are likely to be provoked by important stresses in the scapula, due to the poor muscle state, combined with the weakening of the bone induced by the implant. A 3D numerical model of the shoulder, including the prosthesis, was developed with Abaqus CAE to investigate the stresses in the different regions of the joint, when performing certain movement with the arm. The aim of the project is therefore to adapt the model to some known problematic cases, in order to identify the cause of fracture and propose an adapted solution, in function of the initial state of the joint.