Front Matter

Chapter 17 Diagnosis of and Treatment Options for Disorders of the Spine 431

such as the multifidus musculature, which help
with the stability of the spine, and extrinsic
muscles such as the iliopsoas muscle, which
help in more complex motions allowing for
positioning within the axial or appendicular
skeleton. One overriding factor that should be
kept in mind is that all of these activities occur
while the spinal cord remains protected.
Very little attention has been paid to the
extreme conformational variation that occurs
among breeds and individuals within a specific
breed (Figure 17.9). Small dogs have large cer­
vical spinal canals with what seems to be rela­
tively thinner dorsal lamina for their size. The
relative sizes of the spinal canal going from L4
caudally to the sacral vertebrae can vary tre­
mendously. Sacralization of the last lumbar ver­
tebra and lumbarization of the first sacral
vertebra are very common. The tremendous
variation evident in different canine spines
makes it difficult to provide generalizations
about function. Breeding desirable conforma­
tions and using appropriate training regimens
have to be considered in light of these varia­
tions, when considering the canine athlete.
These are likely to be conformations that are
advantageous for competition and competitive
longevity.

Forces that affect the spine

It is quite obvious that the spine can rotate on

one axis and move in all planes and in more

than one plane at the same time at different

points along its length. Although these motions

are critical for day‐to‐day activities, very little

information is available about the actual forces

involved and the limits necessary to protect spi­

nal structures, including the spinal cord, from

damage.

A biomechanical evaluation of L3–L4 in canine

cadavers (Figure  17.10), where most extrinsic

soft tissue structures had been removed from

the vertebrae, has been performed (Smith &

Walter, 1988). Excision of the supraspinous and

interspinous ligaments yielded a decrease in

stiffness in flexion, an increase in the range of

motion of the interspace, and a decrease in the

ultimate flexion bending strength by 62%.

Panjabi and colleagues (1988) studied the in

vivo effects of transecting the supraspinous and

interspinous ligaments in the cervical spine at

C4–C5. In the cervical spine, this injury caused

a decreased range of motion. It is, of course,

hard to compare the two studies as one study

involved cadavers with most soft tissues

removed and the other was on live dogs.

(B)

(A)

Figure 17.9 (A) Lateral radiograph of a normal lumbar spine. (B) Photograph of a normal lumbar spinal column with
the sacrum attached.