- Discussion:
- to evaluate
C1 (
Jefferson), Dens, superior facets of
C2;
- for evaluating
dens fractures, body of
C2, & rotary
C1-
C2 dislocations;
- mach lines - teeth,
C1 arch;
- open mouth view, along w/
lateral view, will reveal
fractures of the dens ;
- atlantoaxial articulation & integrity of dens and body of
C2 are best
seen on the odontoid view;
- this is most technically most difficult film to obtain as it requires
patient to open his mouth as wide as possible;
- lateral masses of
C1 should align over the lateral masses of
C2;
- lateral displacement of masses of
C1 w/ respect to
C2 may indicate
Jefferson or burst fracture of the
Atlas;
- combined lateral mass displacement > 7 mm suggests that transverse
ligament is torn;
-
children:
- overlapping lateral masses can be a normal variant in children and
therefore this view may not allos assessment of whether frx is
stable or unstable;
- Normal Variants of Dens:
(see
dens frx)
- dens may be completely absent, hypoplastic, or incompletely fused to
body of
C2 (lesion called
Os Odontoideum)
-
Os Odontoideum is smaller than normal dens & is fixed to anterior
ring of
C1: 2 move as a unit;
- subluxation and instability are common;
- Assessment of RA Patient:
- state of the odontoid peg and the lateral processes can be assessed
by open mouth views, though disease of the tempomandibular joint
can make this difficult;
- concomitant vertical subluxation may conceal amount of anteroposterior
movement at the atlantoaxial level because broader base of odontoid
peg comes to lie opposite anterior arch of the
Atlas;
- Technique:
- the patient is positioned as for the supine AP;
- central beam directed perpendicular to the midpoint of the open mouth;
- patient should softly say 'ah' to depress the tongue to the floor
of mouth during exposure;
- Normal Case Examples:
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