Page 288 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.7b The axial skeleton – thoracolumbar region 263

VetBooks.ir 1.498 1.499

Fig. 1.498 Sagittal section through several thoracic Fig. 1.499 Chronic and profound epaxial muscle
vertebrae of a neonatal foal that was unable to rise atrophy of the right side of the back of a horse that
following parturition. There is separation at one of was involved in a traumatic episode several years
the vertebral cranial physes. earlier. This had been associated with severe back
pain, muscle guarding and spasm, and rapid onset of
muscle wastage. (Photo courtesy Graham Munroe)

At one end of the severity spectrum, stress fractures 1.500
of the vertebral lamina may show only vague and
low-grade signs of back pain or poor performance.
In contrast, a severely displaced fracture caudal to
T2 will result in hindlimb paralysis, while a complete
but minimally displaced fracture may still allow the
horse to move without overt discomfort, but show-
ing hindlimb paresis, ataxia and severe focal muscle
spasm and guarding. Subsequently, there may be
local or generalised epaxial muscle atrophy due to
chronic disuse or neurological dysfunction of lower
motor neuron pathways (Fig. 1.499). Fractured
articular facets may also lead to a reflex scoliosis ori-
entated towards the fracture or present later in life
with OA pathology of the joint/s (see Osteoarthritis).
Fractured DSPs will usually have swelling, heat,
pain and guarding. This is especially apparent in
the withers, a prominent area at increased risk of
external trauma compared with areas further cau-
dal (Fig. 1.500). Crepitus may be noted if the horse
allows physical palpation or manipulation. Displaced
DSP fragments in the withers remain attached to
the supraspinous ligament and conjoined nuchal
ligament, and therefore horses may present with Fig. 1.500 View from above of a horse that
an apparent reluctance to move the neck or not be had fallen backwards earlier that day. Note the
able to lower their heads to graze. Once the initial swelling over the proximal aspect of the left scapula.
soft-tissue swelling has reduced, there may be long- Radiography confirmed fractures of the DSPs of
standing visible bony deformity at the withers. T4–T7.