Simpliciti IDE Trial; Replacing the Humeral Head in Total Shoulder Arthroplasty

Inclusion Criteria: * Adult subject 22 years or older * Clinical indication for total shoulder replacement due to primary diagnosis of arthritis. Primary arthritis for this study includes osteoarthritis, and/or traumatic arthritis. * Scapula and proximal humerus must have reached skeletal maturity * Subject with a Constant Score ≥ 20 * Willing and able to comply with the protocol * Willing and able to sign the informed consent (or the Legally Authorized Representative will sign for the subject) Exclusion Criteria: * Lack of sufficient sound bone to seat and support the implant such as: 1. Rapid joint destruction, marked bone loss or bone resorption; 2. Destruction of the proximal humerus that precludes rigid fixation of the humeral component; and 3. Osteomalacia * Metal allergies or sensitivity, including a known allergic reaction to implant metals (e.g., nickel) or polyethylene * Infection at or near the site of implantation, including: 1. Glenohumeral joint infection 2. Osteomyelitis * Distant or systemic infection * Medical conditions or balance impairments that could lead to falls * Prior open shoulder surgery on the shoulder to be treated in the study including failed rotator cuff surgery, but excluding successful shoulder arthroscopy * Any full thickness rotator cuff tear at the time of surgery or a nonfunctional rotator cuff * Excessive glenoid bone loss defined by preoperative computed tomography (CT) scans of the shoulder which show insufficient glenoid bone, or insufficient bone identified at the time of surgery * Metabolic disorders which may impair bone function * Nonfunctional deltoid muscle * Neuromuscular compromise condition of the shoulder (e.g., neuropathic joints or brachioplexus injury with a flail shoulder joint) * Known active metastatic or neoplastic diseases, Paget's disease or Charcot's disease * Currently, or within the last 6 months, or planning to be on chemotherapy or radiation * Currently taking \> 5mg/day corticosteroids (e.g. prednisone) excluding inhalers, within 3 months prior to surgery * Female subjects who are pregnant or planning to become pregnant within the study period * In the surgeon's opinion, the subject is unable to understand the study or be compliant with the follow up or have a history of non-compliance with medical advice * History of any cognitive or mental health status that would interfere with study participation * Alcohol or drug abuse * Engages in manual labor or sports activities that could affect shoulder outcome * Currently enrolled in any clinical research study that might interfere with the current study endpoints