Mechanical jaw restriction after zygomaticomaxillary complex fracture: an unusual coronoid-zygomatic relationship

Displacement of an intact mandibular coronoid process lateral to the zygomaticomaxillary complex (ZMC) is a rare complication of ZMC fractures. We report a case of a woman in her early 30s with malar flattening and inability to achieve full mouth closure following a fall from an electric scooter. Her CT scan revealed a comminuted right ZMC fracture with the ipsilateral intact coronoid process displaced laterally to the ZMC. This rare injury pattern produced mechanical restriction of mandibular movement in both opening and closure. Urgent operative management of the ZMC fracture allowed for spontaneous coronoid reduction allowing passive occlusion intraoperatively and active full mouth closure once awake. At the 3-month follow-up, mandibular movement and malar symmetry had fully recovered. This case highlights the importance of considering coronoid displacement in patients with midfacial trauma and mechanical jaw restriction, the value of CT and the role of early surgical management in preventing long-term dysfunction.