Ultrasonographic diagnosis of caudoproximal humeral stress fracture in thoroughbred racehorses.
Authors: Vaughan Betsy, McKerney Erin R, Wollenberger Carolyn, Cloninger Ashton, Spriet Mathieu, Galuppo Larry, Stover Susan M
Journal: Equine veterinary journal
Summary
# Editorial Summary Caudoproximal humeral stress fractures present a significant challenge in racing Thoroughbreds because they can deteriorate to catastrophic full fractures if missed, yet scintigraphy—the current diagnostic gold standard—remains inaccessible to many practitioners due to cost and equipment availability. This clinical case series of seven young Thoroughbreds (aged 2–4 years) evaluated whether high-frequency ultrasonography could reliably detect these stress fractures, comparing findings against radiography and scintigraphy conducted over an eight-year period. Ultrasonography identified 9 of 10 documented stress fractures (including 2 bilateral cases), with characteristic ultrasonographic features including step defects in cortical bone, periosteal callus formation, and abnormal convexity of the caudal humeral neck—findings that aligned well with radiographic evidence of periosteal and endosteal proliferation. Serial imaging in five horses demonstrated that ultrasound could effectively monitor bone remodelling during healing, with four horses successfully returning to racing and two to ridden work. For farriers, veterinarians and other equine professionals, this work suggests that ultrasonography offers a practical, cost-effective alternative or adjunct to scintigraphy for identifying and tracking humeral stress fractures in performance horses, though careful technique focused on the caudoproximal region is essential for diagnostic accuracy.
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Practical Takeaways
- •Ultrasonography is a practical, accessible alternative to scintigraphy for detecting caudoproximal humeral stress fractures in lame racehorses, improving early diagnosis when fractures can still be managed conservatively
- •Characteristic ultrasound findings (step defects, periosteal callus, convex neck contour) enable practitioners to identify these injuries that may progress to catastrophic fractures if missed
- •Serial ultrasound and radiograph monitoring can guide return-to-training decisions and confirm bone healing, reducing unnecessary layup periods while ensuring safety
Key Findings
- •Ultrasonography identified 9 of 10 humeral stress fractures (90% sensitivity) in 7 Thoroughbred racehorses aged 2-4 years
- •Ultrasonographic abnormalities included step defects (5 humeri), periosteal callus/roughening (7 humeri), and abnormally convex caudal humeral neck contour (6 humeri)
- •Serial ultrasonography and radiography successfully monitored bone remodelling and healing progression
- •Four horses returned to racing, two to riding, and one was retired after diagnosis and layup periods of 3-12 months