A total of 20 patients with shoulder osteoarthritis and scheduled for shoulder surface replacement were randomly assigned to two groups. Using the Global CAP prosthesis with two different coatings, 10 patients were treated with Porocoat and the other 10 patients with DuoFix hydroxyapatite (HA). Patients were monitored for a duration of 2 years after the insertion with the purpose of investigating whether or not loosening does happen with surface replacement of the humeral head, and to identify any benefit that might occur from the additional layer of HA on top of the porous surface. Improvements were observed in clinical outcomes for both coatings, however there was no significant difference between the Porocoat and DuoFix groups. The addition of DuoFix HA coating did not improve migration resistance beyond 3 months after surgery.