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224 Section III: Spinal Procedures

cauda equina and foraminal stenosis. The foramina are narrowed atic nerve are most common and involve the caudal thigh mus-
by facetal joint hypertrophy and spondylosis and the vertebral cles and those distal to the stifle. Compression of the pelvic and
canal is narrowed ventrally by the bulging annulus and dorsal lon- pudendal nerves can lead to urinary incontinence (lower motor
gitudinal ligament, and dorsally by the interarcuate ligaments neuron) and fecal incontinence secondary to poor anal sphincter
[1–5,7,9,10]. As such, the compression of vascular and neural tone [1–5,7].
structures seen in DLSS can be caused by any or a number of the
following: transitional and asymmetric vertebra, or hemivertebra Physical Examination Findings
at L7 or S1 [15–20]; sacral osteochondrosis [21–23]; subluxation A thorough orthopedic examination is essential to rule out hip dys-
of the sacral vertebral endplate relative to L7 [1–5]; subluxation of plasia and cranial cruciate ligament rupture, which are common in
the L7–S1 facetal joints [1–5]; narrowing of the intervertebral breeds prone to DLSS. Some dogs have more than one disorder,
foramen secondary to facetal joint hypertrophy [1–5], osteophy- which can complicate diagnosis. In addition, the neurological defi-
tosis and ligamentous hypertrophy [5,7]; synovial cysts [5]; IVD cits seen with DLSS can resemble those seen with degenerative
protrusion [1–5]; narrowing of the spinal canal secondary to pro- myelopathy. Genetic testing for degenerative myelopathy is advised
liferation of the ligamentous structures such as the dorsal longitu- before proceeding with an invasive treatment procedure since both
dinal ligament and interarcuate ligaments [1–5,7]. conditions may exist concurrently.
Physical examination findings specific to DLSS include pain with
extension of the pelvic limbs either individually or concurrently,
Diagnosis pain with dorsiflexion of the tail until it is perpendicular to the lum-
The diagnosis of DLSS begins with a thorough history, and physical, bar spine or beyond (tail jack), pain elicited during the lordosis test,
orthopedic and neurological examinations. Electrodiagnostics pain with rotation of the lumbosacral spine, and pain with direct
[24,25], radiographic imaging, possibly with contrast studies and palpation of the lumbosacral spine while the dog is supported or in
advanced imaging are also typically performed (see Chapter 7). lateral recumbency [1,7].
Survey radiographs are useful but do not provide the information
necessary for definitive diagnosis and treatment planning. Radiography and Contrast Studies
While the ligamentous structures and the IVD are not visible on
History and Clinical Signs routine radiographs, these can demonstrate changes such as sacral
Pain is the most common sign of DLSS, resulting in varying subluxation, osteophyte formation at the facetal joints, ventral and
degrees of pelvic limb gait abnormalities. Neurological signs gen- lateral spondylosis deformans, and evidence of discospondylitis
erally occur as the condition progresses and can include proprio- that support a diagnosis of DLSS (Figure 26.2) [26–30]. However,
ceptive deficits, mild paresis, loss of tail function, and the presence of radiographic changes consistent with DLSS do not
incontinence [1–5,7,21]. Neurological deficits related to the sci- always correlate with clinical signs [31,32]. In contrast, the absence

B

A

Figure 26.2 Lateral (A) and ventrodorsal (B) radiographic projections of a dog with DLSS showing facetal joint osteophytes, ventral spondylosis deformans,
sclerosis of the vertebral endplates, and narrowing of the lumbosacral intervertebral space. Source: Courtesy of Dr. N. Fitzpatrick.