The proposed clinical study will enroll patients indicated for standard of care anatomic total shoulder arthroplasty. They will receive all pre operative testing, intra-operative care including all implants and post operative care that is standard of care and specific to the surgeon and patients decisions for care. The only difference between the study groups will be the type of surgical instruments used to place the glenoid guide pin. In all cases the surgeon is able and allowed to use their own surgical judgment to place the guide pin, prepare the bone and place the desired implant. In cases that are randomized to the IRIS group the surgeon can use any and all of the standard instruments or guides provided by the implant manufacturer as the surgeon would use in the group of patients randomized to the standard surgical group. If the surgeon chooses not to use the IRIS instruments then this would be noted as a deviation in plan, the reasons recorded and the patient would be excluded from the study without post operative imaging and there pre - operative and intra - operative data would be analyzed for the purpose of understanding the reasons for failure of the IRIS technology to provide surgical assistance for guide pin placement. For patients included in the post operative data analysis will a study specific shoulder CT scan prior to discharge from the hospital to assess the position of the implant. Deviation in the location and position of the implant as compared plan will be our primary outcome measure. Investigators will compare difference between technologies, differences within and between surgeons and the influence of the severity of the pre operative pathology on the two methods of surgical care.