Easytech Reversed Shoulder System Clinical Study

Inclusion Criteria: 1. Patients are 21 years or older. 2. Patients are skeletally mature as evident by scapula and proximal humerus closure. 3. Patients exhibit clinical indications for primary reverse total shoulder arthroplasty based on physical exam and medical history including the following: osteoarthritis, post-traumatic arthritis, or avascular necrosis. 4. Patients have a massive and non-repairable rotator cuff tear. 5. Patients have a functional deltoid muscle. 6. Patients are anatomically and structurally suited to receive the implants; a. Subject show sufficient bone quality in the humerus bone intraoperatively via the thumb test, guide pin test, humeral punch test, and humeral anchor test as outlined in the surgical technique. 7. Patients with an adjusted Constant Score \< 60 and ≥ 15. 8. Patients are willing and able to comply with the follow-up schedule and evaluation outlined in the protocol. 9. Patient are willing and able to sign the informed consent. Exclusion Criteria: 1. Patients with Body Mass Index (BMI) greater than 40 kg/m2. 2. Patients have one of the following compromising the affected limb: a significant injury to the upper brachial plexus, paralysis of the axillary nerve or a neuromuscular disease compromising the affected limb which would render the procedure unjustifiable. 3. Patients have marked bone loss that would not allow sufficient support of the implant. 4. Patients have a known sensitivity or allergic reaction to one or more of the implanted materials. 5. Patients who are participating concurrently in another clinical study, or have participated in a clinical study within the last 90 days, or intend to during the course of the study. 6. Patients who have an active systemic infection, or an active local infection in or near the target shoulder, or have a previous history of joint infection. 7. Patients with known immunodeficiency. 8. Patients currently taking \> 5mg/day corticosteroids (e.g. prednisone) excluding inhalers, within 3 months prior to surgery. 9. Patients with significant comorbidities as evident by an American Society of Anesthesiologists (ASA) score greater than 3. 10. Patients with active neoplastic disease. 11. Patients with current drug or alcohol abuse, or a history of the same within the last 6 months. 12. Patients with local circulatory problems, (e.g. thrombophlebitis and lymphedema). 13. Patients are pregnant or expect to become pregnant during the duration of the study. 14. Patients with any mental or psychological disorder that would impair their ability to complete the study questionnaires. 15. Patients with any medical condition or other circumstances that might interfere with their ability to return for follow-up visits in the judgment of the Investigator, including any systemic illness, neuromuscular, neurosensory, or musculoskeletal deficiency that would render the patient unable to perform appropriate postoperative rehabilitation. 16. Any condition which, in the judgment of the Investigator, would preclude adequate evaluation of device's safety and performance. 17. Patients with humeral or glenoid fractures. 18. Patients unable to stand from sitting position without the use of their hands/arms. 19. Patients with a history of fragility fractures as defined as any fall from a standing height or less, that results in a fracture. 20. Patients with osteoporosis, osteopenia, Paget's disease, osteomalacia or any other metabolic bone disease; a. Osteoporosis is defined as Simple Calculated Osteoporosis Risk Estimation (SCORE) above 6 and DXA (Dual-energy X-ray absorptiometry) T-score \< -2.5 or QCT (Quantitative computed tomography) T-score \< 80mg/cubic cm. History of a fragility fracture requires that a DXA scan or QCT scan is completed.