140
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Fig 6: A branching fracture involving the cervical facet joint (arrows) at C5-6 is visible on the lateral
radiograph shown in panel A. An oblique image shown in panel B was needed to localize the lesion to
the caudal articular facet of C5 and show the full extent of the fracture. In Panel C, outlines are added
of to identify the articular facets: a = the dashed line identifies the enlarged right caudal articular
process of C5, which contains the fracture (arrow). b = right cranial articular process of C6, c = left
caudal articular process of C5, B = left cranial articular process of C6.
Lateral radiographs of the cervical spine (Figs 1 and 2) are provided to review the
radiographic anatomy. The atlas (C1) is easily distinguished by its lack of a spinous
process and short, blocky shape. It articulates with the occipital condyles cranially
and C2 caudally. The axis (C2) is the longest of the cervical vertebrae and has a
large, easily identifiable spinous process. The dens or odontoid process, protrudes
cranially into and lies upon the floor of the vertebral canal of C1. During
development there are 2 separate centres of ossification in the region of the dens
separating the centrum and interceptum from the vertebral body. These can be
confused with fractures in the growing horse. An additional separate centre of
ossification at the ventral aspect of the caudal epiphysis is present during growth.
This is evident in the images presented here and is best seen in Fig 3. C2 articulates
with C3 via an intervertebral disk between the vertebral bodies as well as via a
dorsally located articular facet joint. The articular facets are flat, oval processes that
form diarthrodal joints in an oblique plane. Other than at C2, where the articular
processes are located only caudally, facet joints are formed at the cranial and caudal
aspect of each cervical vertebral segment. The cranial articular process of each
vertebra forms the ventral portion of the articular facet joint while the caudal
articular process sits medially and slightly dorsally. C3, C4 and C5 are similar in size
and shape and are virtually indistinguishable on radiographs providing impetus for the
use of external radio-opaque markers. They have long vertebral bodies, very small
spinous processes, transverse processes comprised of dorsal and ventral tubercles,
and large cranial and caudal articular processes. C6 is different than the more cranial
cervical vertebrae in that the transverse process is plate-like in appearance. On
lateral radiographs this is seen as a flatter ventral silhouette, which can be used to
distinguish C6 from the adjacent vertebrae. C7 is shorter than the other cervical
vertebrae and has only small transverse processes. A dorsal spinous process may be
present. Throughout the cervical vertebrae, thin, crisply defined radio-opaque lines
dorsal to the body of the vertebra and ventral to the articular processes define the
vertebral canal. Intervertebral foramen, which allow for the passage of spinal nerves,
are seen between the articular facets and intervertebral disk spaces.
Oblique radiographs, (Figs 3–6), are ideally performed with the generator 45–50º
dorsal from straight lateral from either side of the neck (left lateral-45–50°-dorsal to
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