Page 157 - Veterinary diagnostic imaging birds exotic pets wildlife

Chapter 16

Spine, Pelvis, and Hips

III SPINE
These fractures are usually situated in the midback or
Normal Anatomy immediately cranial to the synsacrum. Most of these
injuries can be identified in both standard imaging

The spine of birds, excluding the cervical region, differs planes. A case example is provided in Figures 16-4 and
radically from the spine of mammals, particularly with 16-5.
respect to regional collation. Depending on the species,
there may be consolidation of a series of cranial verte- III PELVIS
brae, termed the notarium, or fusion of a series of caudal
vertebrae, termed the synsacrum, which is a fusiform Normal Anatomy
structure located on the underside of the pelvis. There
is a short tail section, followed by a final fusion, termed The pelvis of most birds resembles an inverted shovel

the pygostyle (Figure 16-1). The pygostyle is an impor- blade as seen from the rear. In the perching position,
tant structure that serves to mount the tail feathers, the pelvis of most birds is directed downward at a
providing critical control surfaces, especially during near-vertical angle. All of its component parts—
takeoff and landing. the ilium, pubis, acetabulum, and ischium—are fused
Even if the fused areas of the spine are ignored, the to one another and form a single pelvic bone, which
nonfused spinal elements are equally complex because in turn is fused to the synsacrum at the level of the
of their accessory processes that stream down the back, ilia. At its cranial origin, the pelvis is about the
overlapping one another like so many icicles adorning width of the spine but tapers broadly once it reaches
a winter’s tree (Figure 16-2). A lateral perspective of the the hips, approximately one-third the way to the tail
same region appears far less confusing (Figure 16-3). (Figure 16-6). Pelvic injuries, including fractures, are
rare.
Fractures of the Central and Caudal
Spinal Regions III HIPS
Nondisplaced Spinal Fractures. The few nondis- Normal Anatomy
placed spinal fractures seen in my practice have gener-

ally been difficult to detect, even with the use of The coxal joints, or hips, of birds are angled forward

magnification radiography. To date, I have not had the just as they are in most mammals (Figure 16-7). Unlike
opportunity to perform computed tomography (CT) mammals, however, the greater trochanter and the
on such a bird, but I suspect CT would prove far more femoral head articulate with the acetabulum (Figure
sensitive. 16-8). Fractures and dislocations are rare. Occasionally,
nestlings fall from their nests when first testing their

Displaced Spinal Fractures. Few birds survive a dis- wings and may fracture their proximal femoral growth
placed spinal fracture long enough to be radiographed. plate.
153

2/11/2008 10:59:33 AM
ch016-A02527.indd 153
ch016-A02527.indd 153 2/11/2008 10:59:33 AM