Prevalence of radiographic changes in forelimb digits and metacarpophalangeal joints of South African endurance racehorses.
Authors: Hollenbach, Robert, le Roux, Smit
Journal: Journal of the South African Veterinary Association
Summary
# Editorial Summary South African endurance racehorses experience remarkably high prevalence rates of forelimb radiographic changes, yet the clinical significance of many findings remains unclear. Researchers radiographed the distal forelimbs of 100 competing endurance horses using seven standard views per limb, with three independent observers evaluating the images to establish point prevalence and inter-rater reliability. The most striking findings were the near-universal presence of dorsopalmar hoof imbalance (95%) and digital axis deviation (91%), with 67% displaying a broken-back proximal interphalangeal joint configuration. Conversely, osteoarthritis of the interphalangeal joints was surprisingly low (16% proximal, 7% distal), and metacarpophalangeal joint osteoarthritis affected 28% of horses, with only 10% bilaterally. Notably, 86% of horses had a hoof-distal-phalanx ratio exceeding 25%—traditionally associated with chronic laminitis—yet none showed supporting radiographic evidence, suggesting this metric may not reliably indicate pathology in endurance populations. For practitioners assessing endurance horses, these baseline prevalence data highlight that many radiographic variations are commonplace in this discipline without necessarily correlating to lameness or elimination risk. The disconnect between structural variation and clinical disease underscores the importance of integrating radiographic findings with clinical examination, biomechanical assessment and performance history rather than treating radiographic changes as definitive indicators of pathology. Future research correlating these changes with age, competitive workload and lameness outcomes would substantially strengthen clinical decision-making in endurance horse management.
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Practical Takeaways
- •Broken back hoof-pastern axis (67% prevalence) is extremely common in South African endurance horses and warrants farriery and management attention; practitioners should consider early intervention strategies
- •MCP joint osteoarthritis (28% prevalence) is a significant concern in endurance athletes; radiographic evaluation of these joints may be warranted in lameness investigations
- •Do not rely solely on hoof-distal-phalanx ratio as a diagnostic indicator of chronic laminitis in endurance horses; clinical signs and additional imaging must be considered
Key Findings
- •95% of endurance horses showed bilateral dorsopalmar hoof imbalance and 91% had digital axis deviation
- •Extended proximal interphalangeal joints (broken back conformation) were present in 67% of horses, the most common abnormality
- •Metacarpophalangeal joint osteoarthritis was present in 28% of horses, with 10% bilateral involvement
- •Hoof-distal-phalanx ratio >25% was present in 86% of horses but did not correlate with chronic laminitis signs, questioning its reliability as a laminitis indicator in this population