restricted mouth opening (trismus) with cheek swelling after a blow raises concern for a displaced zygomatic arch or zygomaticomaxillary complex fracture.

If conventional radiographs are being requested, obtain:

However, the preferred investigation in a patient with this presentation is non-contrast CT of the maxillofacial bones with thin axial images and coronal/sagittal reconstructions, rather than relying on X-rays. The ACR facial-trauma criteria rate CT maxillofacial without contrast as usually appropriate for suspected midface injury. Plain films can miss overlapping midface fractures; Cummings Otolaryngology Head and Neck Surgery notes that CT has largely replaced them for middle- and upper-face trauma.

Urgently assess visual acuity, diplopia, eye movement, malocclusion, facial numbness, and airway status. New double vision, reduced vision, severe pain with eye movement, vomiting, altered consciousness, or worsening swelling warrants emergency assessment.

So the answer is: SMV plus Waters views. If only one plain-film view is feasible for an isolated zygomatic arch injury, choose SMV.

In current practice, proceed to CT maxillofacial bones without contrast if the examination is significant or X-rays are abnormal, because it defines displacement and associated orbital/midface injury better.