32 adult patients with shoulder osteoarthritis were included in this trial to compare two humeral head resurfacing implants (HHRI): the Copeland HHRI and the Global C.A.P. HHRI. Implant migration, periprosthetic bone mineral density (BMD), and length of glenohumeral offset (LGHO) were assessed via radiostereometric analysis (RSA), in addition to clinical questionnaires (Constant score and Western Ontario Osteoarthritis of the Shoulder Index). Findings indicated minimal migration using either implant, and comparable clinical results. Significant differences between groups were noted in periprosthetic BMD and LGHO, in which the Copeland HHRI exhibited significantly greater perioprosthetic BMD at 1 and 2 years, but significantly greater LGHO.