Page 416 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.9 Muscle disorders of the horse 391

VetBooks.ir 1.760 Diagnosis
History and clinical examination are important,
especially palpation of affected muscles for pain,
swelling and spasm in acute cases and atrophy/
fibrosis in chronic cases. Visual appraisal is useful.
Full lameness examination is paramount. Muscle-
stimulating machines may identify specific muscle
injuries. Thermography, nuclear scintigraphy and
ultrasonography can all help locate the site of injury
and, with the latter, determine the extent of dam-
age (Figs. 1.761, 1.762) and monitor healing. The
initial ultrasonographic appearance is of hypoecho-
genic haemorrhage, which becomes progressively
more echogenic as the haematoma organises and
fibrosis occurs. Mild increases in plasma muscle
enzyme activity may be present, depending on the
severity of the muscle damage, but are often within
normal limits in the case of mild tears.
Tears can be classified according to the severity:

• First-degree – mild muscle soreness and low-
grade inflammation and swelling with few
localising clinical signs.
Fig. 1.760 View of the quarters of a Thoroughbred
racehorse that has returned from exercise with • Second-degree – partial tear with obvious
an acute-onset right hindlimb lameness. There clinical signs if a superficial tear is present.
is swelling of the right hindlimb caudal gluteal • Third-degree – complete tear with loss of
muscles, which was painful on direct palpation and, function.
after ultrasonography examination, was confirmed
as grade 2 muscle damage. (Photo courtesy Management
Graham Munroe) The type of treatment depends on the specific
injury and the stage at which it is diagnosed.
Acute injuries may benefit from cold therapies and
NSAID therapy to provide pain relief and reduce
defect where there is a complete tear. In addition, inflammation. Many of the treatments involve
complete muscle tears may subsequently present physiotherapy techniques and machines (e.g. laser,
with an abnormal limb position or gait abnormality. therapeutic ultrasound, TENS, electromagnetic
In the forelimb the most commonly affected sites therapy, massage, stretching and manipulation to
are the biceps brachii, the brachiocephalicus and improve range of motion), although objective data
pectoral muscles and the superficial digital flexor showing an association with improved outcome in
muscle/tendon junction. In the hindlimb, the biceps the horse is lacking. These are combined with box
femoris, semimembranosus and semitendinosus, rest (first-degree tears, 7 days; second-degree tears,
adductor, gluteal, quadriceps and gastrocnemius 1–3 weeks; third-degree tears, several months) and
muscles are most commonly involved. Muscle spasm a controlled graduated exercise programme once
and pain are common in the thoracolumbar region the acute stages are over. Resolution of the primary
secondary to a hindlimb lameness or primary spinal problem is essential before any secondary muscle
or sacroiliac injury. injury can be treated.