Hemiarthroplasty is an open procedure where one part (humerus) of the shoulder joint is replaced with a synthetic implant (metal or pyrocarbon). This is commonly performed in cases such as an unsalvageable fracture of the arm bone (proximal humerus), or shoulder arthritis in young patients who are not suitable for total joint replacement. In this procedure, your surgeon will remove the damaged part of the bone and replace it with the implant.