Standing CBCT, Fetlock and 2 years-old

Prospective, longitudinal assessment of subchondral bone morphology and pathology using standing, cone-beam computed tomography in fetlock joints of 2-year-old Thoroughbred racehorses in their first year of training

Sarah A. Ciamillo, Kathryn B. Wulster, Taryn M. Gassert, Dean W. Richardson, Kara A. Brown, Darko Stefanovski, Kyla F. Ortved

Background:
Catastrophic injuries in the fetlock joints of Thoroughbred racehorses often result from stress-induced bone injuries. Early detection of subchondral bone pathology could prevent irreversible damage and fractures. This study investigates the use of standing, robotic cone-beam computed tomography (CBCT) to monitor changes in subchondral bone morphology and pathology over a year of race training in young Thoroughbreds.

Methods:
This observational cohort study included 41 two-year-old Thoroughbred racehorses at the beginning of their training. CBCT and radiographs of the fetlock joints were taken at 0, 6, and 12 months. Subchondral bone sclerosis (hyperdensity) and pathology (areas of hypodensity surrounded by hyperdensity) were assessed longitudinally at predefined anatomical sites.

Results:
-Sclerosis: Significant increases in subchondral sclerosis were observed in the medial and lateral condyles of the third metacarpal/metatarsal (MC3/MT3) and parasagittal grooves over time.

-Pathology: Subchondral bone pathology prevalence increased over time, particularly in the medial and lateral palmar condyles of MC3/MT3, lateral parasagittal grooves, and ridges of the proximal phalanx (P1). The first 6 months of training saw the most rapid accumulation of pathology.

-Diagnostic Performance: CBCT was superior to conventional radiography in detecting subchondral bone lesions.

Limitations:
Attrition of study participants due to relocation or retirement reduced the sample size at later time points.
Variation in training regimens and schedules was uncontrolled.
Bone mineral density could not be directly measured using CBCT, relying instead on hyperdensity as a proxy.

Conclusions:
Standing CBCT is an effective tool for early detection of subchondral bone changes, offering significant advantages over radiography. This technique allows for timely interventions to modify training regimens, potentially reducing the risk of severe injuries in racehorses. Further studies correlating findings with clinical outcomes like lameness are recommended.

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