Objective—To evaluate effects of toe grabs, exercise
intensity, and distance traveled as risk factors for subclinical
to mild suspensory apparatus injury (SMSAI)
in Thoroughbred racehorses and to compare incidence
of severe musculoskeletal injury (MSI) in horses
with and without SMSAI.
Design—Nested case-control study.
Animals—219 Thoroughbred racehorses racing or in
Procedure—Racehorses were examined weekly for
90 days to determine incidence of suspensory ligament
injury and monitor horseshoe characteristics.
Every horse's exercise speeds and distances were
recorded daily. Conditional logistic regression was
used to compare exposure variables between incident
case (n = 25) and selected control (125) horses.
Survival analysis was used to compare time to MSI
for horses with (n = 41) and without (76) SMSAI.
Results—The best-fitting logistic model for the data
included age (< 5 vs ≥ 5 years old), toe grab height the
week of injury (none vs very low, low, regular, or
Quarter Horse height), and weekly distance the week
preceding injury (miles). Although the 95% confidence
intervals for all odds ratios included 1, the odds
for SMSAI appeared to increase with the presence of
a toe grab, higher weekly distance, and age ≥ 5 years.
Horses that had SMSAI were significantly more likely
to have a severe MSI or severe suspensory apparatus
injury than were horses that did not.
Conclusions and Clinical Relevance—Results suggest
that pre-existing SMSAI is associated with development
of severe MSI and severe suspensory apparatus
injury. Modifying training intensity and toe grab
height for horses with SMSAI may decrease the incidence
of severe MSI. (J Am Vet Med Assoc 2001;