In older people with osteoporotic bone, achieving stable fixations with a locking plate or satisfactory fixation of the tuberosities to a hemiarthroplasty can be challenging. In such cases, the initial implantation of a reverse shoulder arthroplasty has become a widely performed procedure. However, the evidence supporting the use of the implant and its various modifications is weak. More than 20 years after the approval by the American Food and Drug Administration, only two small randomized trials have been published, both failing to demonstrate clinically important differences in favor of reverse shoulder arthroplasty compared to non-surgical treatment. Indications have drifted without proper testing in randomized trials. Even an engineering masterpiece like the reverse arthroplasty needs rigorous clinical testing in the relevant population to document the benefits and harms and to prevent unnecessary surgery. Despite numerous observational studies, unbiased estimates of treatment effects are still needed to guide treatment decisions. This is especially important for implants and procedures that alter the human anatomy. In this chapter, I will discuss one of the most unique implants in orthopedics from an evidence-based perspective.