Relate radiological appearances to clinical features
Follow the three 'McGrigor-Campbell' lines to look for the common fracture patterns
The most common fracture configurations are - isolated zygomatic arch fracture - 'tripod' fracture - and 'blowout' fracture
Check for the 'teardrop' and 'eyebrow' signs
Systematic approach
There are many complex overlapping bone structures in the face with a highly variable appearance. Radiological findings must be related to clinical features as it is easy to misinterpret appearances.
Standard views
Occipito-Mental (OM) and Occipito-Mental at 30 degrees angulation (OM30).
This view is acquired at 30º from horizontal with the patient in the same position as for the OM view
Each infra-orbital canal is part of the floor of the orbit - these carry the maxillary division of the trigeminal nerve which can be injured as the result of fracture
Note that each maxillary antrum is clear (black)
Other visible structures include the mandible and the odontoid peg
McGrigor-Campbell interpretation lines
Facial bone fractures result from direct trauma and usually follow one of only a small number of patterns. 'McGrigor-Campbell' lines can be used as a simple aid to interpretation. The eye follows these lines to check for these common fracture patterns.
The ' McGrigor-Campbell lines' are visible on OM and OM30 views and can act as anatomical references to assess the facial bones for injury
Upper line - (Red) passes through the zygomatico-frontal sutures (asterisks) and across the upper edge of the orbits
Middle line - (Orange) follows the zygomatic arch (elephant's trunk), crosses the zygomatic bone and follows the inferior orbital margins to the opposite side
Lower line - (Green) passes through the condyle (1) and coronoid process (2) of the mandible and through the lateral and medial walls of the maxillary antra on each side
Midline - used to assess symmetry
Facial fractures
The most common configuration of facial fractures include isolated zygomatic arch fractures, 'tripod' fractures, and orbital 'blowout' fractures.
Disruption of the middle McGrigor-Campbell line is due to a comminuted fracture of the right zygomatic arch
Following the upper and lower lines shows no fracture
'Tripod' fractures
Trauma to the zygoma may result in impaction of the whole bone into the maxillary antrum with fracture to the orbital floor and lateral wall of the maxillary antrum.
The displaced zygoma is detached from the maxillary bone, the inferior orbital rim, the frontal bone at the zygomatico-frontal suture, and from the zygomatic arch. The result is said to liken a 'tripod', but in reality these fractures are often more complex than is appreciated on plain X-ray. 'Quadripod' would perhaps be a more accurate term as four fractures may be visible.
A fluid level of blood seen in the maxillary antrum may be the only obvious sign of fracture
'Tripod' fracture
A - Widened zygomatico-frontal suture
B - Zygomatic arch fracture
C - Orbital floor fracture
D - Lateral maxillary antrum wall fracture
Note
The zygomatico-frontal suture (A) has a variable normal appearance
Widening of the suture - if seen alone - does not indicate a fracture
Orbital 'blowout' fractures
Trauma to the orbit may lead to increased pressure in the orbit such that the thin bone of the orbital floor bursts. This manifests as the 'teardrop' sign which is due to herniation of orbital contents into the maxillary antrum.
On the left a 'teardrop' of soft tissue has herniated from the orbit into the maxillary antrum
Orbital emphysema
Occasionally a 'tripod' or 'blowout' fracture will cause a leak of air from the maxillary antrum into the orbit. This can have the appearance of a dark 'eyebrow'.
Fractures are visible of the lateral wall of the maxillary antrum and of the orbital floor
Air has leaked into the orbit and is seen as an area of comparative low density - the 'eyebrow' sign
There is also increased soft tissue density due to swelling, and increased density of the maxillary antrum due to blood
Fracture mimics
X-ray appearances can easily be misinterpreted unless a systematic approach is used to look for the common fracture patterns. Any suspected injury should be correlated to the clinical features. Overlying structures such as sutures should not be interpreted as fractures.
