Shoulder patient specific instrument

A method of guiding a glenoid prosthesis, the method comprising:

• pre-operatively determining a position and an orientation of a guide feature of a glenoid guide based on a scapula of a specific patient, the glenoid guide comprising:
• the guide feature comprises a tapered lumen configured to receive a pin guide;
• at least three arms having a first end coupled with the guide feature and a second end disposed away from the guide feature;
• at least three peripheral pegs, each peripheral peg extending from the second end of a corresponding arm and comprising an engagement surface configured to engage the scapula of the patient;
• and
• a strut extending laterally from the guide feature, the strut comprising a positioning opening;
• engaging the glenoid guide with the scapula;
• and
• inserting a pin having an axis through the guide feature to or through the scapula.