The SMR Stemless Reverse is intended for total, primary shoulder joint replacement by reducing pain and restoring shoulder articular mobility function. This is a prospective, multi-center, randomized, controlled trial to demonstrate non-inferiority of the SMR Stemless Reverse to the SMR Reverse Shoulder System.

Patients with joint dysfunction who continue to experience significant symptoms despite an appropriate course of non-operative management are eligible. Patients will be considered enrolled into the study when an ICF has been signed, all inclusion criteria are met and no exclusion criteria are present including intraoperative exclusion criteria, and the patient is randomized into either the SMR Stemless Reverse (investigational) group, the SMR Reverse Shoulder System (control) group or is part of the roll-in population. Enrollment is expected to take approximately 24 months.

Inclusion Criteria:

1. Age ≥ 22 years of age

2. Skeletally mature as evident by scapula and proximal humerus closure

3. Candidate for primary total shoulder replacement in a grossly rotator cuff deficient joint with severe arthropathy (disabled shoulder), when clinical indications based on physical exam and medical history including one or more of the following:

   1. Arthritis with rotator cuff tear not reparable
   2. Irreparable rotator cuff tear
   3. Rotator cuff tear arthropathy
   4. Severe osteoarthritis and rotator cuff deficiency or stiff shoulder
   5. Significant glenoid or socket side bone deformed or loss
   6. Reoccurrence of instability or a chronic shoulder dislocation
   7. Any other medical reason that the investigator determine that subject is a good candidate for a reverse total shoulder arthroplasty

Exclusion Criteria:

1. BMI > 40 kg/m2
2. Previous contralateral shoulder surgery within 3 months of enrollment or that requires active treatment (i.e. surgery or brace)
3. Had surgery in the targeted shoulder within last 12 months of enrollment, except diagnostic arthroscopy without procedures
4. Had surgery in lower limbs (such as hip or knee) within last 6 months of enrollment
5. Corticosteroid injections in the ipsilateral shoulder within 3 months of enrollment
6. Complete deltoid muscle insufficiency
7. Glenoid retroversion great than 25 degrees based off a 2D axial CT scan
8. History of/or signs and/or symptoms of local or systemic infection including but not limited to septicemia; osteomyelitis
9. Neurologically confirmed nerve lesion compromising shoulder joint function
10. Poor meta-epiphyseal bone stock compromising stability of the implant including but not limited to humeral head fracture, iatrogenic glenoid fracture, severe osteoporosis
11. Metabolic disorders which may impair fixation and stability of the implant including but not limited to uncontrolled diabetes mellitus with an HbA1C > 7.5%
12. Extended bone loss after previous surgery defined as: complete bone loss of greater and lesser tuberosity
13. Meta-epiphyseal bony defect (including large cyst)