As the main aim of the study is to build a prediction model, the study size is calculated to observe a minimal number of events by potentially predictive variable. We consider here 7.5 events by independent variable (Vittinghof and McCulloch, 2007) and eight independent variables. According to literature review, we estimated that 35% of adults included in this study would spontaneously use their affected upper arm in activities of daily living six months after discharge. According to these data and considering 10% of protocol deviations, we calculated that 192 subjects will have to be included in the study. The inclusion duration will be 30 months.