Comparison of Two Resurfacing Prostheses in the Treatment of Osteoarthritis of the Shoulder

Inclusion Criteria: 1. Patients with shoulder osteoarthritis with cartilage defect of the caput humeri and not the glenoid cavity 2. Aged 18 years or older and fit 3. Informed, written consent - Exclusion Criteria: 1. Patients found unsuitable preoperatively for a resurfacing prosthesis 2. Patients aged 85 or older 3. Patients with rheumatoid arthritis 4. Patients who previously had undergone shoulder alloplasty or other major shoulder surgery (more than just diagnostic arthroscopy) 5. Patients unable to avoid NSAID after surgery 6. Patients requiring regular systemic steroid treatment 7. Female patients taking hormone substitution 8. Patients with metabolic bone disease 9. Severe shoulder instability with large rotator cuff defect ( will often necessitate special prosthesis components or even major soft-tissue surgery) 10. Female patients in the fertile age range who do not use safe anti-conception (oral contraception, intrauterine devices, depot gestagens, vaginal hormone rings) -