Page 298 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.7b The axial skeleton – thoracolumbar region 273

VetBooks.ir also allows ultrasound-guided injections to be per- the ventral surface of thoracic or lumbar vertebrae.
The ease of ultrasound scanning these joints
There is no evidence that the intervertebral discs are
formed, confirming the significance of abnormali-
ties observed. The close proximity of the spinal also affected.
cord increases the risk of catastrophic spinal nerve Aetiology/pathophysiology
blocking and therefore diagnostic therapy with cor- The formation of bone at the sites of soft-tissue
ticosteroid is a safer alternative. Back pain improves attachments on the ventral surface of the vertebrae
significantly within 7 days of corticosteroid medica- may represent a form of entheseophytosis, with wear
tion if clinically significant OA is present, although and tear of the connective tissues leading to new
concurrent regional pathology may diminish the bone formation. This is supported by the fact that
perceived improvement. the condition tends to be seen in older horses.
In humans, the disease may cause pain by pressure
Management from proliferating bone on nerve roots, but equine
Corticosteroids such as methylprednisolone or tri- vertebral anatomy and function differ considerably,
amcinolone can be injected directly into the tissues with much narrower intervertebral discs and less
overlying the joints, preferably using small volumes movement between the vertebrae (see Fig. 1.477).
(e.g. 1 ml per site). Bisphosphonate drugs are also These differences may explain why spondylosis in
helpful in conjunction with all of the previously horses is often asymptomatic. The bone prolifera-
described non-specific symptomatic methods of tion occurs in regions occupied by the ventral lon-
managing back pain. gitudinal ligament and the outer annular fibres of
the intervertebral disc, ventral to the disc spaces,
Prognosis and may extend to form a solid plate of bone on the
The prognosis for a horse with back pain due to facet ventral surface of the thoracolumbar vertebral col-
joint OA depends on the number of joints affected umn. Lesions are most common in the region T9 to
and the severity of the pathology, the presence of T15, with usually multiple sites affected, especially
concurrent lesions such as DSP impingement, as well in severe cases. In the majority of horses, the bone
as the type of work being performed and the ability proliferation appears to cause no pain. Occasionally,
of the horse and rider. Poor thoracolumbar flexibility the plate of proliferative bone can fracture, leading
and pain caused by multiple affected joints, particu- to an acute onset of clinical signs.
larly if accompanied by further lesions elsewhere in
the vertebral column, are negative prognostic signs. Clinical presentation
Successfully resolving pain while simultaneously This rare clinical condition (3.4% of 670 cases with
increasing epaxial muscle strength and mobility can back pain in one USA report) has frequently been
lead to good results; however, there is always a risk encountered as an incidental finding when the dorsal
that pain will recur when medication wears off, espe- thorax has been radiographed for reasons other than
cially if other risk factors for back pain are ignored suspected thoracolumbar pain and in post-mortem
(e.g. lameness). studies of back pathology. The clinical signs are
those seen in other chronic back pain conditions and
SPONDYLOSIS may include back stiffness, poor hindlimb impul-
sion, poor jumping ability and reluctance to flex and
Definition/overview extend the thoracolumbar vertebral column. In one
Spondylosis (‘spondylosis deformans’; ‘ventral spon- study, 60% of cases had concurrent osseous back
dylosis’; ‘vertebral spondylosis’) in humans is defined pathology, which may complicate the presentation.
as a degenerative disease of the intervertebral discs
and vertebrae and proliferation of bone on the Differential diagnosis
ventral and ventrolateral surfaces of the cervical, Other osseous or soft-tissue pathology of the thora-
thoracic or lumbar vertebral column. In the horse, columbar vertebral column can cause some or all of
the term refers to the new bone that is produced on the clinical signs described.