In 1970 Neer first published his results on humeral head replacement for proximal humeral fractures. During the past 3 decades, our ability to treat these fractures with arthroplasty has evolved as a result of our better understanding of proximal humeral anatomy, innovations in prosthetic design, and meticulous surgical technique. Fracture reduction with stable internal fixation is a basic surgical principle for all fractures. When this is achieved, early mobilization of the injured extremity can minimize joint stiffness and muscle atrophy. When prosthetic arthroplasty is the preferred treatment of a proximal humeral fracture, correct height and version are necessary with cement fixation of the stem. Many fracture systems now incorporate internal and external guides that can help place the prosthesis in correct version and height. The current challenge is to restore proximal humeral geometry with stable internal fixation of the tuberosities. At present, tuberosity complications account for the majority of early failures and poor outcomes (Table I and Table II). This article reviews the pertinent anatomic landmarks that help achieve a proper reduction of the tuberosities and defines the biomechanical and clinical consequences of malunion and nonunion.