Summary:In the treatment of acute proximal humerus fractures, primary prosthetic humeral replacement arthroplasty is employed for four-part fractures and fracture dislocations, selected three-part fractures in older patients with soft bone, head splitting fractures, and head impression fractures involving >40% of the articular surface. A muscle-sparing deltopectoral approach, proper soft-tissue length, correct prosthetic height and version, meticulous tuberosity repair, and early postoperative passive range of motion are all vital to successful reconstruction. Our institutional experience over 40 years with 174 reported cases of humeral head replacement for acute fracture has had a high proportion of satisfactory results. The most significant factor associated with failure is lack of patient compliance with aftercare.