To cite: Kassam K, Messiha A. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2013202633 DESCRIPTION We report a case of a patient with a 9-day history of trismus measured at 9 mm (figure 1). The trismus occurred immediately after an alleged assault with punch injuries to the face. Note the flattening of the malar process on the left hand side of the face. X-rays of the facial bones showed a depressed fracture of the zygomatic arch with a medial rotation of the zygomatic complex (figure 2). Orthopantogram X-ray clearly showed an additional fracture of the coronoid process (figure 3). Clinically, the depressed arch fracture has impinged on the coronoid process producing the limitation in mouth opening. The Henderson Classification is a commonly used system to describe zygomatic fractures. It ranges from Henderson I, which is an undisplaced fracture at any site, to Henderson VII, which is a comminuted fracture. This is a case of Henderson IV type, as it is a tripod fracture with a distracted frontozygomatic suture which could also be palpated clinically. There is a high probability that the conservative treatment in this case would lead to temporomandibular pseudoankylosis characterised by trismus-restricted mandibular movements, resulting from factors outside the joint. Treatment will involve elevation of the arch with a two-point fixation at the zygomatic buttress placed via an intraoral approach and at the frontozygomatic suture placed via an upper blepharoplasty incision. The fractured coronoid can be removed if unstable and preventing mouth-opening or quite often left due to its strong muscle attachments. The operation will restore the mouth-opening and improve the cosmetic defect (figure 4).