Functional and radiological outcomes of arthroscopic scapular spine bone block "diamond" fixation for recurrent anterior shoulder instability with subcritical glenoid bone loss.

Background: Arthroscopic glenoid reconstruction with free bone blocks reduces recurrence in anterior shoulder instability. The scapular spine bone block has been described to address subcritical glenoid bone loss (GBL), though its clinical outcomes are still unclear. This study aimed to report the functional and radiological outcomes of patients with anterior shoulder instability and GBL <15% who underwent arthroscopic glenoid reconstruction using a scapular spine bone block fixed with knotless suture anchors in a "diamond" configuration. Methods: A tricortical spine bone graft was harvested. Two knotless all-suture anchors were centrally placed at the glenoid defect. Each anchor included 1 suture for repair and another for transport. The repairs suture from the anchors were interconnected through two holes, creating a bridge over the graft tunnels. The remaining suture limbs were inserted into a third knotless anchor midway between the initial two, establishing a stable configuration for secure fixation. Range of motion, patient-reported outcomes, return to sport, instability recurrence, complications, and reintervention were assessed at a minimum 2 years postoperatively. The glenoid surface area was measured preoperatively, postoperatively, and at a 2-year follow-up, with graft resorption evaluated at a 2-year follow-up. Results: Three patients were included. The GBL ranged from 8% to 13%. Range of motion was similar between sides at the 2-year follow-up. Patients scored higher in patient-reported outcomes from baseline to the 1-year and 2-year follow-ups. All patients returned to sports within 8 months. No recurrent instability or reinterventions occurred. At 3 months postoperatively, all patients achieved graft union, with complete glenoid surface area remodeling at 2-year follow-up. Conclusion: Arthroscopic scapular spine bone block fixation using knotless suture anchors in a "diamond" configuration is effective and safe for treating recurrent anterior shoulder instability with <15% GBL, facilitating an early return to sports.