Page 281 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

256 CHAPTER 1

VetBooks.ir horse in the back. Horses can be totally normal with- pain, pelvic pathology, dental pain, gastric ulcers or
other forms of gastrointestinal pain.
out apparent loss of performance until a sudden onset
of severe topical pain and guarding in the dorsal tho-
racolumbar area; a minority of these horses become Diagnosis
dangerous to handle. Symptoms vary hugely between The diagnosis is made following a detailed passive
individuals and within the same individual over time. and dynamic assessment of the musculoskeletal
Recent time off work will often ameliorate clinical system. Diagnostic analgesia is indicated to prove
signs while a highly skilled rider can mask or improve the connection between clinical and imaging find-
a horse’s exhibition of pain. Breed differences should ings. Unfortunately, the depth and inaccessibility
be taken into account, both in symptoms of pain and of the spinal structures, the different types of pain
in the response to examination. encountered, as well as the proximity of these to the
The whole horse should be examined as horses spinal cord, often contraindicate this intervention.
with back pain frequently exhibit concurrent lame- Diagnostic therapy is widely used as a practical alter-
ness and pelvic, neck or even dental problems. Some native for some conditions in the back.
horses have clinically silent back pathology that As everywhere, clinical and imaging abnormalities
becomes symptomatic when they develop pain else- correlate poorly. Radiography and ultrasonography
where in the body or limbs, confusing the clinical are important complimentary imaging modalities for
picture. Recognising and successfully treating the epaxial structures, but both have limitations. With
distant pathology sometimes causes back pain to increasing body weight and muscle depth, the radia-
resolve in such horses. This functional interconnect- tion scatter progressively limits visualisation and the
edness is called kinetic chain dysfunction in human image quality deteriorates. Imaging thoracic DSPs is
sports medicine. Using NSAIDs diagnostically for possible using modern mobile high-frequency units,
a short period can provide useful information with where lateral to lateral projections are the mainstay
which to distinguish horses with compensatory and (Fig. 1.483), but the vertebral bodies and lumbar
primary causes of back pain. For example, lame DSPs may be obscured in adult horses and ponies.
horses with distal tarsal pain and compensatory Obtaining ventrolateral 20° to dorsolateral oblique
(secondary) lumbar epaxial tenderness are likely to views of the ipsilateral caudal thoracic facet joints is
resolve back pain fairly quickly after commencing more challenging, requiring a focused grid or alumin-
oral NSAID treatment. Horses with kissing spines ium wedge filter and much higher power (Figs. 1.484,
(primary) are unlikely to resolve back pain as quickly 1.485). Visualising lumbar facet joints with radiog-
or as profoundly. raphy is rarely possible in any animal larger than a
Gastric ulcers occur commonly and arranging for pony and requires optimal equipment and technique.
gastroscopy to be performed is helpful. Solely treat- Ultrasonography provides good visualisation of the
ing gastric ulcers is unlikely to solve problems but dorsal spinal structures and epaxial muscles, but
is a useful adjunctive symptomatic treatment where no hypaxial structures can be seen. The supraspi-
extensive grade 3 or 4/4 ulcers are identified in the nous ligament and tops of the DSPs can be viewed
squamous or pyloric regions. in good detail with a high-frequency linear tendon
probe (Figs. 1.478, 1.486). The dorsal and trans-
Differential diagnosis verse spinous processes, along with the facet joints,
Primary muscle pain from tack or riding technique, dorsal lamina and deeper epaxial muscles, require a
trauma, impingement of DSPs, facet joint OA, low- frequency curvilinear probe (Fig. 1.487).
supraspinous desmitis and ventral spondylosis. Note Where symptoms and imaging diverge, the
that more than one condition is often present; for physiological imaging modalities of gamma scintig-
example, 132 horses (25%) of 526 horses with DSP raphy and thermography are both popular and can
impingement also had facet joint uptake on scintig- provide useful complimentary information. Gamma
raphy, and six horses also had concurrent facet joint scintigraphy in the thoracolumbar area is of most
and ventral spondylosis. Secondary muscle pain use for acute bone injury, such as following trauma,
from hindlimb lameness, forelimb lameness, neck or in detection of stress fractures (Fig. 1.488).