Total hip arthroplasty is currently one of the most widely performed surgical interventions. However, surgical failures still occur and can lead to severe consequences. The main cause of implant failure is aseptic loosening, related to a deficient osseointegration of the implant. Therefore, a good primary stability is mandatory to achieve bone ingrowth and long-term stability. In press-fit acetabular cups, the initial stability is achieved through frictional forces by inserting the cup in an under-reamed cavity. In the presence of acetabular defects, the effective contact area can be extremely reduced, and the choice of the implant can drastically affect the cup stability.