TSA v RSA in Osteoarthritic Shoulders With Greater Than 15 Degrees of Retroversion

Inclusion Criteria: 1. Diagnosis of idiopathic shoulder OA. 2. Patients who have failed standard non-surgical management of their shoulder OA who would benefit from a shoulder arthroplasty. Failed medical management will be defined as persistent pain and disability despite adequate standard non-operative management for at least 6 months. Medical management will be defined as: a) The use of drugs including analgesics and nonsteroidal anti-inflammatory drugs, b) Physiotherapy consisting of stretching, strengthening and local modalities (ultrasound, cryotherapy, etc.), c) Activity modification 3. Imaging, and intra-operative findings confirming advanced glenohumeral cartilage loss 4. Patients with a glenoid deficiency and \>15 degrees of glenoid retroversion up to a maximum of 26 degrees of glenoid retroversion (i.e. -15.1, -17, -20…etc.) 5. 65 years of age and older Exclusion Criteria: 1. Active joint or systemic infection 2. Rotator cuff arthropathy 3. Significant muscle paralysis 4. Charcot's arthropathy 5. Major medical illness (life expectancy less than 1 year or unacceptably high operative risk) 6. Unable to understand the consent form/process 7. Pregnancy 8. Psychiatric illness that precludes informed consent 9. Unwilling to be followed for the duration of the study 10. Retroversion cannot be surgically corrected to within 10 degrees of neutral 11. History of previous shoulder surgery on affected side 12. Rheumatoid arthritis in the affected shoulder