Many studies have been published that discuss patient outcomes after shoulder arthroplasty.8, 14-17 These studies are limited by small patient populations, limited follow-up, and heterogeneity of patient populations and surgical indications. No study has compared Total Shoulder Arthroplasty with Reverse Shoulder Arthroplasty in the treatment of osteoarthritis in the population older than 70 years of age. The Shoulder and Elbow service at Washington University is uniquely qualified to conduct a study of this type given the exceptionally large surgical volume of shoulder arthroplasty (over 350 shoulder arthroplasty cases performed annually), access to Ultrasonography for imaging of all study participants and a robust and well-organized research infrastructure that can execute established research protocols.