In a patient who fell and struck the right side of the head and jaw and now has trismus (inability to open the mouth), should I order an emergent CT scan of the head and facial bones or obtain plain radiographs (X‑ray)?

Order CT Maxillofacial (Facial CT)

In a patient with trismus following head and jaw trauma, you should order a CT scan of the maxillofacial region (facial CT), not plain radiographs. Given the mechanism (fall with head strike) and clinical finding of inability to open the mouth, you also need a CT head to evaluate for intracranial injury 1.

Why CT Over X-ray

CT maxillofacial is superior to radiography for mandibular and temporomandibular joint (TMJ) fractures, with nearly 100% sensitivity compared to 66-92% for plain films 1. This matters critically because:

• Condylar and subcondylar fractures (which cause trismus) are frequently missed on plain films but easily detected on CT 1
• Posterior mandibular fractures are particularly difficult to visualize on radiographs 1
• CT detects comminution and displacement that directly change surgical management 1
• 67% of mandibular fractures involve two separate sites—CT is essential to identify the second fracture 1

The Trismus Factor

Trismus (inability to open mouth) in this context strongly suggests:

• Condylar or subcondylar fracture with displacement
• TMJ fracture-dislocation (rare but can occur with lateral head trauma) 2, 3
• Temporal bone fracture affecting TMJ stability 3

Plain radiographs have significant limitations for these injuries—they cannot adequately assess displacement in the ramus/condyle region where "the degree of displacement can be subtle" 1.

Head CT is Also Mandatory

39-68% of patients with mandibular fractures have associated intracranial injuries 1. The mechanism (fall striking head) combined with jaw injury mandates evaluation for:

• Intracranial hemorrhage
• Skull fractures
• Temporal bone fractures (which can cause trismus even with intact TMJ) 3

Practical Imaging Algorithm

1. Order CT head AND CT maxillofacial simultaneously during initial trauma evaluation 1
2. Use multiplanar reformations (axial, coronal, sagittal) for complete fracture assessment 1
3. No IV contrast needed—does not aid fracture detection 1
4. Look specifically for:
   • Condylar/subcondylar fractures
   • Second mandibular fracture (present in 67% of cases)
   • Temporal bone fractures
   • Intracranial injury

When Plain Films Might Be Acceptable (But Not Here)

The ACR guidelines mention panoramic radiographs (OPG) only for "low clinical suspicion of injury" 1. Your patient has:

• High-energy mechanism (fall)
• Head strike
• Trismus (functional impairment indicating significant injury)

This is NOT low suspicion—this warrants CT.

Common Pitfall

Don't order just a head CT assuming it will show facial fractures adequately. While head CT detects 95% of facial fractures, it "often only partially images fractures of the midface" and misses critical details about displacement and comminution that affect surgical planning 1.

Bottom line: Order both CT head and CT maxillofacial now. The combination provides complete evaluation of both intracranial injury risk and the mandibular/TMJ pathology causing trismus, with sensitivity far superior to plain radiographs for the injuries most likely present 1.