Inclusion Criteria:  Greater than 18 years of age. Scheduled to undergo total shoulder arthroplasty surgery. Scheduled pre-operative CT imaging of the shoulder and the surgical plan includes open exposure of the glenoid.  Exclusion Criteria:  Previous shoulder surgery involving the glenoid. No clinically indicated pre-operative CT imaging. Pregnancy (current or planned). Current or planned participation in other research, or having a clinical condition that would result in cumulative annual radiation exposure exceeding the regulatory limit (30 mSv) from all sources.