A New Tool for Preoperative Planning of Reverse Total Shoulder Arthroplasty

The Reverse Total Shoulder Arthroplasty (RTSA) is a complex surgical procedure also due to the difficulty in correctly positioning all the components of the prosthesis. Malpositioning of the prosthesis, in fact, can lead to various complications such as scapular notching, early mobilization, instability and reducing of the range of movement (ROM). Preoperative planning with 3D imaging and patient specific instruments can be very useful tools to help surgeon in selecting the optimal position of implant components. Aim of this work is to develop a procedure based on a fully parametric CAD system that simulates the shoulder joint to identify the optimal positioning of the humeral and glenoid components of the prosthesis. In particular, the proposed system allows to find the optimal cutting angles of the humerus head and the glenoid cavity so to best fit the patient’s bone structure and the prosthesis components and, consequently, to improve the range of movement. The system allows to create, in a semi-automatic way, CAD assembly models composed of the patient shoulder bones and different reverse shoulder prostheses. For each assembly different positions of the components of the prosthesis can be evaluated and various scenarios of movements can be simulated. In this way it is possible to identify the optimal positioning of the prosthesis for each patient in the preoperative stage. The proposed procedure has been tested with two types of prosthesis and two patients. Obtained results demonstrated that an optimal positioning of prosthesis an improve ROM up to 27%.