A bone block procedure is performed arthroscopically for recurrent dislocation or instability of the shoulder. This procedure utilizes a bone graft to address the defect either in front (anterior bone block) or back (posterior bone block) of glenoid bone. Your surgeon will harvest the graft as a small piece of bone from another part of your body (pelvic bone or collar bone), this will then be secured to the defect in the glenoid with screws or sutures.