Page 1037 - Adams and Stashak's Lameness in Horses, 7th Edition

Occupational‐Related Lameness Conditions 1003

reduced biochemical evidence of muscle damage in Suspensory Desmitis
Thoroughbreds with recurrent exertional rhabdomyoly­ Forelimb suspensory desmitis (SD) is common in
VetBooks.ir of rhabdomyolysis in racing Thoroughbreds. Although endurance horses, affecting both the proximal area and
sis. In addition, dantrolene reduced recurrent episodes
3
1
branches. Hindlimb SD is less common but likely has a
dantrolene use during competition is prohibited, it is
used in an attempt to prevent recurrent myopathy similar pathogenesis, and the treatment options are
during training and/or long‐distance transport of elite identical. SD usually develops when local footing con­
Arabian endurance horses predisposed to myopathy sists of deep sand, soft soil, or mud. Hence, in areas such
prior to resuming work. the United Arab Emirates, SD is the most common cause
Muscle spasms or cramps and muscle strains are also of lameness in endurance horses. The diagnosis is sus­
quite common in the sport. The gluteal muscles are com­ pected based on palpation of the limb and is confirmed
monly affected, but other muscle groups, including the by ultrasonography (Figure 9.45). The author’s impres­
gracilis, lumbar, triceps, biceps, forearm, and pectoral sion is that medial/lateral hoof imbalance predisposes
muscles, may be involved. Occasionally horses with endurance horses to suspensory branch desmitis. With
muscle spasms are acutely painful; they may collapse branch lesions, usually only one branch is affected;
and show signs similar to those of acute colic. These therefore, notable swelling may be evident on palpation
individuals usually benefit from prompt analgesic treat­ compared with the opposite branch or leg. In contrast,
ment. Most often an α‐2 agonist (e.g. detomidine, xyla­ lesions of the proximal suspensory and body may be less
zine) with or without a narcotic (butorphanol) is more obviously swollen, and diagnosis is usually based on
effective and safer compared with high doses of NSAIDs, sensitivity to palpation and ultrasound. Subtle, recurrent
considering the likelihood of significant concurrent lameness associated with proximal SD may require
dehydration. Massage therapy, stretching or walking, diagnostic nerve blocks followed by ultrasonography
and topical heat may help treat muscle cramps. On‐site for confirmation.
serum biochemical analysis in these patients is prudent After an acute injury, the character of the ultra­
because it may reveal electrolyte imbalances, necessitat­ sonographic lesion severity may worsen over time, so
ing correction. serial examinations to follow lesion progression are
Muscle pain affecting the back and skin sensitivity of recommended. Response to topical ice therapy can be
the saddle and girth regions is common in endurance dramatic and is warranted for the first 24 hours’ post‐
horses. It is likely that both are related to rider imbal­ injury. This should be followed by intermittent ice
ance and poor saddle fit and compensatory back pain water or cold‐water therapy and bandage support. After
may develop secondary to hock lameness. In the neck rehydration, NSAID treatment for the first 5–10‐day
region, sensitivity of the strap muscles in front of the post‐injury is typical. The prognosis for return to func­
shoulder (brachiocephalicus m.) is very common and tion is good in horses with mild desmitis. Those with
likely develops as a consequence of forelimb lameness minimal to no ultrasonographic changes may only
(usually in the feet or ankles) or fatigue. need 3–4 weeks of stall rest and hand walking before
More rarely, frank muscle tears may cause acute gradually returning to work under saddle, with an
lameness. Occasionally, local hematomas may form. additional 4–6 weeks of walk/light trot intervals prior
Rest and NSAIDs (post‐rehydration) usually lead to full to returning to training work. With significant lesion
recovery. size, long‐term rest (minimum 6–8 months) is prudent.
Horses with significant desmitis are best managed

Figure 9.45. Ultrasonographic image
of the lateral suspensory branch from an
endurance horse that developed grade 3
lameness after 83 miles of competition.
Enlargement and fiber disruption were
minimal, and the horse returned to work
after several weeks of rest. Source:
Courtesy of Dr. Patty Doyle.