This study will compare total shoulder arthroplasty (TSA) reverse shoulder arthroplasty (RSA) procedures, in the context of a prospective, randomized-controlled trial to determine the optimal treatment in patients 65 years of age and older, and equal to or less than 15 degrees of glenoid retroversion, who have glenohumeral osteoarthritis.

Osteoarthritis (OA) of the shoulder is a disease resulting from the wearing down of cartilage over time. OA can be the cause of pain and dysfunction and is a growing occurrence in the investigator's aging population. TSA or RSA are common surgical procedures used to treat patients with shoulder OA. TSA is able to keep the "natural anatomy" of the shoulder and involves replacing the worn-out ball and socket shoulder joint with prosthetic components. TSA is performed today with high success rates, however, complication rates associated with TSA remain prevalent, particularly when the arthritis is associated with bone erosion on the glenoid (socket).

RSA is an alternative surgical procedure commonly used and involves replacing and reversing the ball and the socket (i.e. opposite of TSA). RSA is typically performed in patients with a rotator cuff deficiency and more severe OA. Though RSA procedures show marked increase in clinical and functional outcomes, evidence of its long-term results are sparse, and as such is typically reserved for when treating an older patient population.

Few research studies have compared these different surgical techniques to one another, in the older patient population.

This research will provide surgeons with new information regarding the best treatment for patients in this population.

This Randomized Controlled Trial (RCT) will compare TSA and RSA procedures in those 65 years of age and older, who have equal to or less than 15 degrees of glenoid retroversion, in an effort to determine which approach produces better functional outcomes and improved quality of life in this patient population.

Primary Objective: Determine the difference in disease specific quality of life between patients diagnosed with glenohumeral OA who undergo either a TSA or RSA as measured by the Western Osteoarthritis of the Shoulder (WOOS) score at 24-months and 5-years post-operative.

Secondary Objectives: i) Determine the difference in disease specific quality of life between patients diagnosed with a glenohumeral osteoarthritis who undergo a shoulder replacement with RSA or TSA as measured by the Constant score, the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment form (ASES), the EuroQol Group EQ-5D-5L score, pain (using a Visual Analog Scale), and Subjective Shoulder Value (SSV) at 24-months and 5-years post-operative as well as adverse events, and health care utilization.

ii) To determine the survivorship of the components as measured by the degree of radiographic lucencies and component alignment determined by a CT scan at 1- and 5-years post-surgery.

Clinical Relevance: Shoulder OA results in pain and dysfunction, which negatively impacts quality of life. As such, determination of superior treatment approach will lead to significant improvement in quality of life, and cost savings through avoidance of recurrence and/or reoperation, as well as decreased morbidity for patients in this population.

Inclusion Criteria:

1. Patients who have failed standard non-surgical management of their idiopathic shoulder osteoarthritis 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 6 months. Medical management will be defined as:

   1. The use of drugs including analgesics and non-steroidal anti-inflammatory drugs
   2. Physiotherapy consisting of stretching, strengthening and local modalities (ultrasound, cryotherapy, etc.)
   3. Activity modification

2. Imaging, and intra-operative findings confirming advanced glenohumeral cartilage loss

3. Patients may present with a glenoid deficiency and \

IPD will not be shared with other researchers, who are not participating in the study.