This is a mono-center trial. Patients in the process of pre-operative care of a reverse shoulder arthroplasty (CT Scan already available as part of the care course in supine position) will be offered the study. A localizer ultrasound will be performed during surgical consultation or the day before the surgery in standing position (duration: 1/2 day). This consultation takes place during the course of the surgical consultation or when the patient is admitted the day before his surgical procedure.
The objective of this study is to analyse the positioning of the scapula in standing position and compared to the supine position (CT scan) in 3 dimensions (3 rotations of the scapula) using a non-radiant, portable system, combining an ultrasound probe with marker and a camera integrated into a Tablet for the three-dimensional location of the marker (probe).