This study examines the mechanical behaviour and biodegradation performance of an orthopaedic staple manufactured of a magnesium alloy (WE43) by using a finite element modelling approach. A U-shaped staple and surrounding bone were discretised into four degradation statuses, based on an empirically determined correlation of the corrosion over time, to allow a realistic simulation of material loss through time. Static structural and fatigue analyses showed that despite progressive wall thinning, the staple kept the stress level below the critical value and showed acceptable deformation and accumulated fatigue damage, which was below the failure level during the healing interval. These results indicate that magnesium staples can achieve stable fixation on a temporary basis with gradual resorption to decrease the need for revision surgeries.