Objective—To determine clinical characteristics of
and outcome in Thoroughbred racehorses with tibial
or humeral stress fractures.
Animals—99 Thoroughbreds with tibial or humeral
Procedure—Information obtained from the medical
records included history, signalment, and clinical, radiographic,
and scintigraphic findings. Outcome was
determined by interviewing trainers, performing follow-
up examinations, and analyzing race records.
Results—Seventy-four tibial stress fractures were
identified in 61 Thoroughbreds, and 48 humeral
stress fractures were identified in 39 Thoroughbreds
(1 horse was included in both groups). Tibial stress
fractures occurred most commonly in 2-year-old or
unraced horses. Fractures were located in 1 of 3 sites
in the tibia (most commonly, the caudolateral cortex
of the mid-diaphysis) and 1 of 4 sites in the humerus
(most commonly, the caudodistal cortex). Forty-four
of 58 (76%) tibial stress fractures and 18 of 32 (56%)
humeral stress fractures were identified radiographically.
Humeral stress fractures involving the caudodistal
cortex were not detected radiographically.
Treatment consisted of rest and exercise restriction,
and 49 of 61 (80%) horses with tibial stress fractures
and 30 of 39 (77%) horses with humeral stress fractures
returned to racing. Humeral stress fractures
recurred in 6 horses.
Conclusions and Clinical Relevance—Results suggested
that in Thoroughbred racehorses, tibial stress fractures
occurred most commonly in unraced 2 year olds, whereas
humeral fractures occurred most commonly in older
horses that had raced previously. The prognosis for racing
following treatment was good. (J Am Vet Med Assoc