The purpose of the study is to investigate fixation to bone and the clinical results following shoulder resurfacing arthroplasty. The study will compare results between an implant made of Cobalt-Chrome(CoCr) and an implant made in pyrocarbon.

Inclusion Criteria:

• Primary or secondary osteoarthritis of the shoulder
• Age 40-75 years
• Patient capable of giving informed consent
• Patient agrees to comply with the study plan

Exclusion Criteria:

• Destruction of the proximal humerus
• Insufficient bone stock
• Deficient rotator cuff or earlier failed surgery of the rotator cuff
• Large muscle defects or insufficient blood supply in the affected arm
• Neuromuscular disorders
• Infection, untreated malignancy or transmittable disease preventing the patient from fulfilling the study
• Patient unwilling to comply with study regulations
• Patient with earlier allergic reaction to pyrocarbon
• Patient with known metastatic disease
• Patient who has been treated with more than 10 mg corticosteroids (e.g. Prednisone) daily within 3 months from surgery.
• Patient participating in other clinical study
• Patient in need of glenoid replacement