Osteoarthritis (OA) of the shoulder is a disease resulting from the wearing down of cartilage over time. OA can produce pain and dysfunction at the affected joint and is a growing occurrence in an aging population. Total shoulder arthroplasty (TSA) is a surgical treatment used to treat patients with shoulder OA which 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).

Given the high rate of revisions associated with TSA treatment in the setting of glenoid bone erosion, a number of surgical strategies have been developed. These surgical techniques include eccentric reaming which involves removing bone from the front of the socket, augmented glenoid component implantation, and posterior bone grafting to compensate for glenoid bone loss, and reverse shoulder arthroplasty. Few research studies have compared these different surgical techniques to one another. Previous studies have been limited to case series with small sample sizes and respective designs. This study is being conducted to determine which approach produces better outcomes. For the purpose of this study we will be comparing total shoulder arthroplasty techniques a) augmented glenoid component and eccentric reaming and b) augmented glenoid component and bone grafting in participants with advanced glenohumeral osteoarthritis.

Patients who have 10-15 degrees of retroversion will be randomly assigned to one of two standard of care treatment groups: TSA with eccentric glenoid reaming or TSA with augmented glenoid component implantation.

Patients whose condition involves > 15 degrees of retroversion will be randomly assigned to one of two standard of care treatment groups: TSA with augmented glenoid component implantation or posterior glenoid bone grafting.

The primary objective will be measured by the Western Ontario Osteoarthritis of the Shoulder Index (WOOS) score pre-operatively and at post-operative time intervals (i.e. 3, 6, 12 and 24 months).

Secondary Objectives: i) 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 between study arms in both age groups.

ii) To determine the difference in disease specific quality of life between treatment allocations in both age groups as measured by the Constant score, the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment form (ASES) and the EuroQol Group EQ-5D-5L score pre-operatively and at post-operative time intervals (i.e. 3, 6, 12 and 24 months), as well as adverse events, and health care utilization.

Patient Population The target population is both men and women of any age with advanced osteoarthritis of the glenohumeral joint who are considered by the treating surgeon to be a candidate for shoulder replacement. The type of arthritic process will not be considered a deciding factor. The arthritis must be amenable to treatment using either a humeral head replacement (stemmed or stem-less), or a standard total shoulder replacement.

Inclusion Criteria

1. Patients who have failed standard non-surgical management of their 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. Patients will present with a glenoid retroversion between 10-26 degrees.

3. Imaging, and intra-operative findings confirming advanced humeral head cartilage loss, with or without glenoid cartilage loss.

4. Age 18 years or older

Exclusion Criteria

1. < 10 degrees / > 27 degrees of glenoid retroversion
2. Active joint or systemic infection
3. Rotator cuff arthropathy
4. Significant muscle paralysis
5. Charcot's arthropathy
6. Major medical illness (life expectancy less than 1 year or unacceptably high operative risk)
7. Unable to understand the consent form/process
8. Pregnancy
9. Psychiatric illness that precludes informed consent
10. Unwilling to be followed for the duration of the study
11. Retroversion cannot be surgically corrected to within 10 degrees of neutral
12. History of previous shoulder surgery on affected side
13. Rheumatoid arthritis in the affected shoulder