A system for implanting a shoulder prosthesis in a scapula of a patient, comprising: (a) a primary glenoid component (20; 120) including an anchor (40; 130) adapted to be implanted within the scapula of the patient in a primary surgical procedure, (b) a second glenoid component (60; 160) adapted to be implanted within the scapula of the patient and including: a platform (62; 162) having an anchor (64; 164) extending therefrom, and at least one of an anatomic bearing and a glenosphere component which can be attached to the platform, the anatomic bearing having a smooth bearing surface upon which a natural or prosthetic humeral head can articulate, and the glenosphere component having a surface that articulates upon a bearing surface of a humeral cup and which forms a reverse glenoid component, in which the geometry and shape of the anchor of the second glenoid component are similar to the geometry and shape of the anchor of the primary glenoid component, characterised in that the second glenoid component is a secondary glenoid component which is adapted to be implanted within the scapula of the patient in a revision surgical procedure, and the system includes a tool guide which can be positioned over the primary glenoid component when it is implanted in a patient's glenoid, for guiding a tool to penetrate and bore through the primary glenoid component and the glenoid surface of the scapula to remove the anchor portion of the primary glenoid component which is implanted in the patient's glenoid, in which the similarities between the geometry and shape of the anchor of the second glenoid component and the geometry and shape of the anchor of the primary glenoid component are such that the anchor of the second glenoid component can be received in the cavity within the patient's glenoid which results from the removal of the anchor portion of the primary glenoid component when performed using the tool guide. (a) a primary glenoid component (20; 120) including an anchor (40; 130) adapted to be implanted within the scapula of the patient in a primary surgical procedure, (b) a second glenoid component (60; 160) adapted to be implanted within the scapula of the patient and including: a platform (62; 162) having an anchor (64; 164) extending therefrom, and at least one of an anatomic bearing and a glenosphere component which can be attached to the platform, the anatomic bearing having a smooth bearing surface upon which a natural or prosthetic humeral head can articulate, and the glenosphere component having a surface that articulates upon a bearing surface of a humeral cup and which forms a reverse glenoid component, in which the geometry and shape of the anchor of the second glenoid component are similar to the geometry and shape of the anchor of the primary glenoid component, a platform (62; 162) having an anchor (64; 164) extending therefrom, and at least one of an anatomic bearing and a glenosphere component which can be attached to the platform, the anatomic bearing having a smooth bearing surface upon which a natural or prosthetic humeral head can articulate, and the glenosphere component having a surface that articulates upon a bearing surface of a humeral cup and which forms a reverse glenoid component, in which the geometry and shape of the anchor of the second glenoid component are similar to the geometry and shape of the anchor of the primary glenoid component,