two common views of the face?
- occipitomental (OM)
- occipitomental 30 (OM30)
OPG and mandibles
- OPG machine will show almost all mandibular #s
- # of symphis menti may not be shown
- an oblique mandible may also be performed, but varies between hospitals
What is the radiogrpahic baseline?
- aka the orbitomeatal baseline
- runs from the outer canthus of the eye to the external auditory meatus
OM Projection
- (how is the radiographic baseline positioned?)
- (where is the petrous ridge projected?)
- the radiographic baseline is angle 45 degrees up - chin and nose resting on the detector
- the petrous ridge is projected inferiorly of the maxillary sinusmmmmmmmmmmmmmmmm
What is the anthropological baseline?
- inerior border of the orbit to the superior border of the EAM
- splits the skull into superior and inferior aspects
what is the auricular baseline
splits the skull into anterior and posterios halves
-perpendicular to the anthropological baseline
name the anatomy:
- glabella
- naison
- symphysis menti
- external occipital protuberance
- external auditory meatus
- outer canthus of the eye
- glabella: area between eyebrows
- naison: depression inferior of glabella
- symphysis menti: where the two halves of the mandile articulate
- External occipital protuberance: on the midline at the inferior aspect of the occiput
- external auditory meatus: the hole that is surrounded by the pinna of the ear
- outer canthus of the eye: the lateral aspect of the eye, where the upper and lower eyelids meet
what is the interpupillary line?
horizontal line that connects the pupils of the eyes, used for checking if there is left/right tilt
name the sutures of the head
- coronal suture: connects frontal and parietal bones
- sagital suture: connects the parietal bones
- squamos suture: connects parietal and temporal boens
- lambdoid suture: connects parietal boens with occipital
OM Orbits Positioning
Patient is positioned as for OM (but 20 degree instead) with a perpendicular tube or for a PA positiont(radiographic baseline perpendicular to detector) with 20 degree caudaul angulation
letterbox collimation
OM positioning
- patient faces the detector
- radiographic baseline (EAM - outer canthus of the eye) raised 45 degree
- centre above EOP
- collimate to include zygomatic arches, mandible, superior skin surface
- 75kVp 20mAs
- use a grid
OM30 positioning
same positioning as OM but with a 30degree caudal angle
What are the McGrigors Lines?
used to assess # patterns of facial bones
ALWAYS COMPARE INJURED SIDE WITH UNINJUERD SIDE
line 1: passes along the upper orbital borders and through the zygomato-frontal sutures
- LOOK FOR #, WIDENING OF THE ZYGOMATICOFRONTAL SUTURE AND ANY FLUID LEVEL IN THE FRONTAL SINUS
line 2: superior border of the zygomatic arch, along the inferior margin of the orbits, and the superior aspect of the opposite zygomatic arch
- LOOK FOR # OF ZYGOMATIC ARCH, # OF INFERIOR RIM OF THE ORBIT, A SOFT TISSUE SHADOWN IN THE ROOF OF THE MAXILLARY ANTRUM
line 3: inferior margin of the zygomatic arch, down the lateral wall of the maxillary antrum, continue along the inferior margin of the antrum, across the maxilla, up the opposite lateral wall of the maxilla and along the inferior aspect of the opposite zygomatic arch
-LOOK FOR # OF THE ZYGOMA AND LATERAL ASPECT OF THE MAXILLARY ANTRUM. FLUID LEVEL IN THE MAXILLARY ANTRUM
Midface injuries
- (what is common?)
- (what is rare?)
- (what is a tripod #?)
- isolated # of the zygomatic arch are common
- isolated # of the zygomatico-frontal suture or of the body of the zygoma are rare
- tripod #: combinatio of widening of the zygomatico-frontal suture, # of the zygomatic arch, # through the body of the zygoma (this is seen as a break in the inferior margin of the orbit and the lateral wall of the maxillary antrum)
What is a blow-out #?
- (how does it occur?)
- in an isolated blow-out #, the inferior orbital rim is intact but the walls and floor of the orbit may #
- some of the orbital contents may herniate downwards
- results from a direct compressive force e.g, a fist
- this herniation causes an opaque TEARDROP HANGING FROM THE ROOF OF THE MAXILLARY ANTRUM
What is the black eyebrow sign?
this is a black (lucent) line at the superior aspect of the orbit
- this is caused by air entering the orbit from a sinus because of a #
the mandible
- (what should it be thought of as?)
- (50% of # are what?)
- (frequent site of #?)
- the mandible should be thought of as a ring structure
- 50% of mandible #s are bilateral
- # of the manibular condyles are frewquent and should be carefully examined
If a OPG appears normal, a PA mandible may be required (radiogrpahic baseline perpendicular, centre middle of neck)
Le Fort Fractures
1 - low level or horizontal fracture: separates teh ahrd palate and the alveolar process from the middle face
2- pyrimidal or subzygomatic: # line involves the nasal bones and the orbital floor, passing through the walls of the maxillary sinus and the paltes of the sphenoid. Separates the mid portion of the face from the cranium and lateral aspects of the face
3- high transverse or suprazygomatic #: # line involves the nasal bones at a high level, the cross the medial wall of the orbit. THe sygomatic is also #
