A 32-year-old male construction worker sustains a crush injury to his right tibia when a steel beam falls on his leg at the worksite. On arrival at the emergency department, there is a 3 cm laceration over the fracture site with visible bone fragments protruding through the wound. Soft tissue damage is limited to skin and muscle, with no vascular or nerve injury. The fracture is comminuted. What is the Gustilo classification of this open fracture?