This is a multi-center study assessing postoperative outcomes associated with hemiarthroplasty with pyrocarbon (hPYC) versus anatomic total shoulder arthroplasty (aTSA). Once eligibility criteria is met, the subject will be randomized to one of the two study arms. Subjects will be followed for ten years. Clinical and patient-reported outcome measures (PROMs) will be assessed.

Inclusion Criteria:

1. Fluent in English language
2. Willing to sign an informed consent form
3. Willing to comply with all study procedures and be available for the duration of the study
4. Age 40 to 65 years
5. In good general health as evidenced by medical history
6. Surgical indication of glenohumeral osteoarthritis 7. In the opinion of the surgeon, there is clinical equipoise for the subject to be implanted with a humeral hemiarthroplasty with pyrocarbon or anatomic total shoulder arthroplasty

Exclusion Criteria:

1. Presence of Walch Type C or D glenoid
2. Presence of a glenoid that could not be reconstructed with the anatomic glenoid resurfacing components
3. Presence of extreme preoperative glenoid deformity including uniplanar retroversion deformity >30 o or severe biplanar deformity (retroversion >20 o and inclination > 10 o).
4. Workers' compensation case
5. Presence of full-thickness rotator cuff tear
6. Known allergic reactions to components of the study product(s)
7. History of consistent narcotic use within three months of surgery
8. History of chronic oral corticosteroid use
9. History or current drug or alcohol abuse
10. In the surgeon's opinion, the subject will be non-compliant with the study protocol.