46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
141
right lateral-ventral oblique and right lateral-45–50°-dorsal to left lateral-ventral
oblique). Alternatively, the generator can be moved 45–50° ventral from lateral to
achieve a similar view (Withers et al. 2009b). This method will result in increased
distance between the facets and the detector and therefore more m agnification on
the radiographs. In the ideal situation, the detector will be perpendicular to the x-ray
beam to reduce geometric distortion of the anatomy but depending on the available
equipment this may not be possible. This is particularly notable in the caudal spine
due to the shoulder. In some circumstances, mechanical constraints such as the
height of the x-ray generator may not allow more than 30º of obliquity; this does not
preclude the production of these images although interpretation is made somewhat
more difficult as there is less separation of the paired symmetric structures. Markers
should be placed indicating the surface highlighted by the obliquity. In Figures 3–5,
the x-ray beam travelled from right dorsal to left ventral during production of the
example radiographs. This resulted in highlighting of the left dorsal aspect of the
vertebrae as noted by the L marker.
Oblique radiographs result in separation of the paired anatomic structures (facets
and transverse processes) and provide the opportunity to acquire orthogonal
projections thereby enabling better evaluation of the individual joint for fracture,
congenital abnormalities and degenerative changes. Obliquity separates the articular
facets such that one side is projected dorsally to the contralateral one and the other
joint is projected over the spinal canal. The dorsally projected articular processes
are generally clearly identified. The ventrally projected articular processes are more
difficult to evaluate because of superimposition, however, the evaluation of this joint
is critical as the beam angle is tangential to the facet joint space. Well-positioned
oblique radiographs will show the joint space, joint margins and subchondral bone
surfaces, critical for the assessment of joint disease. In Figure 6, 2 radiographs are
presented which provide an example of a cervical articular facet fracture which was
visible on lateral radiographs, but the laterality, configuration and extent of the
fracture was not fully appreciated until oblique views were taken. Similar to the
articular facets, the transverse processes are separated on oblique radiographs; one
is projected ventrally, often overlying the trachea. Transverse process fractures are
less commonly reported and are unlikely to be associated with neurological
abnormalities but could explain instances of pain and stiffness in the cervical region.
In conclusion, while plain, lateral radiographs of the cervical spine can aid in diagnosis
of a number of pathologic processes that cause pain and neurological symptoms in
the horse, the addition of oblique images to the radiographic study will allow for
better characterisation of lateralised pathology. Although initially daunting, with
careful anatomic study, interpretation of these oblique radiographs can become
routine and greatly improve diagnostic ability.
References
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Adams, S.B., Steckel, R. and Blevins, W. (1985) Diskospondylitis in five horses. J. Am. vet.
med. Ass. 186, 270-272.
Berg, L.C., Nielsen, J.V., Thoefner, M.B. and Thomsen, P.D. (2003) Ultrasonography of the
equine cervical region: a descriptive study in eight horses. Equine vet. J. 35, 647-655.
Colbourne, C.M., Raidal, S.L., Yovich, J.V., Howell, J.M. and Richardson, J.L. (1997) Cervical
diskospondylitis in two horses. Aust. vet. J. 75, 477-479.
Down, S.S. and Henson, F.M.D. (2009) Radiographic retrospective study of the caudal
cervical articular process joints in the horse. Equine vet. J. 41, 518-524.
Furr, M.O., Anver, M. and Wise, M. (1991) Intervertebral disk prolapse and diskospondylitis
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