Mirror Medacta Shoulder System Pivotal Trial

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)