The posterior guide was inserted from the posterior portal, using the arthroscope from the anterosuperior portal. Care was taken to introduce the guide parallel to the glenoid surface and to have the bone tunnels perfectly perpendicular to the anterior glenoid neck according to Taverna et al. technique (Taverna et al., 2014). The hook was passed parallel to the glenoid face to avoid damage to the articular surface, and it was advanced over the anterior edge (Fig. 1a). The guide’s hook was placed at the center of the anterior glenoid defect (Fig. 1b). It was mandatory to align the glenoid guide with the posterior and anterior glenoid rims. Once the guide was positioned, a bullet was placed in each hole of the guide (Fig. 2). A 2.8 mm sleeved drill was placed in each bullet and advanced until it came out from the anterior aspect of the glenoid. The drills were placed 5 mm below the cortical edge of the glenoid rim, parallel to one another and 10 mm apart. The inner drill was removed leaving the cannulated outer sleeve. Once drilling was completed, the bullets were removed posteriorly. Flexible looped guidewires were introduced into the joint by passing one wire through each sleeve in a posterior to anterior direction. Each guidewire was retrieved using a loop grasper, which was passed through a cannula introduced through the rotator interval. The wires were separated and stored. The drill sleeves were removed after this step was completed. At this point, the inferior 8 mm anterior cannula was removed and was replaced by a metal cannula with a diameter of 15 mm suitable for passing the graft attached to the two buttons.Fig. 1Left shoulder, anterior on the right and posterior on the left, scope from antero-superior portal, hook guide from posterior portal. The Hook guide is parallel to the glenoid surface (a) and in the center of bone defect (b) (HH: humeral head, GL: glenoid)Fig. 2Left shoulder. The guide is positioned posteriorly on the glenoid neck and two bullets are placed in the guide’s holes