The purpose of this study is to demonstrate safety and efficacy of the Mirror Medacta Shoulder System in total shoulder arthroplasty.

Inclusion Criteria:

• Age ≥ 18 yr
• Clinical indication for anatomic primary total shoulder replacement due to osteoarthritis and/or posttraumatic arthritis
• Willingness and ability to comply with study protocol

Exclusion Criteria:

• Medical condition or balance impairment that could lead to falls
• Prior rotator cuff surgery
• Cuff tear arthropathy/insufficient rotator cuff
• Insufficient bone quality which may affect the stability of the implant
• Neuromuscular compromise of shoulder or other disabilities affecting the maximum functional outcomes
• Weight bearing shoulder due to wheel chair, crutches, rollator at the time of operation
• Active metastatic or neoplastic disease at the shoulder joint
• Chemotherapy treatment/radiotherapy within 6 mo before surgery
• >5 mg/day of corticosteroids, excluding inhalers, within 3 years before surgery
• Pregnancy or plan to become pregnant during study period
• Inability to understand study or a history of noncompliance with medical advice
• Alcohol or drug abuse
• Current enrollment in any clinical research study that might interfere with this study
• Metal allergies or sensitivity.
• Previous or current infection at or near the site of implantation.
• Current distant or systemic infection
• Patient, whose infomed consent form should be taken in an emergency situation
• ONLY for women of childbearing age: a positive pregnancy test (urine / blood)