Do radiographic signs of sesamoiditis in yearling Thoroughbreds predispose the development of suspensory ligament branch injury?

Reasons for performing study Sesamoiditis is believed to be associated with injury to the suspensory branch attachment and is a common radiographic finding in yearling Thoroughbreds. No study has investigated relationships between yearling sesamoiditis and subsequent development of suspensory ligament branch injury (SLBI) in early racehorse training. Objectives To establish the prevalence of SLBI within a population of juvenile training racehorses and retrospectively investigate relationships between clinical signs of SLBI and sesamoiditis to determine if sesamoiditis is a risk factor for clinical suspensory branch injury. Study design Retrospective case control study. Methods Presale radiographs of 291 clinically normal yearling Thoroughbreds were reviewed for sesamoiditis and graded using 3 objective scales. Medical records encompassing the first year of race training were reviewed to identify cases of SLBI and the remaining unaffected controls from the cohort. Statistical analysis determined the relationship between sesamoiditis and the development of SLBI during training. Results The prevalence of SLBI was 9.97%. Case and control horses demonstrated a similar prevalence of sesamoiditis overall but SLBI cases demonstrated increased severity of sesamoiditis on yearling radiographs compared with unaffected controls. This significant relationship between sesamoiditis and cases of SLBI was only observed using one of the 3 scales. Using that scale, sesamoids exhibiting more pronounced sesamoiditis on yearling radiographs were 5 times more likely to develop SLBI in the adjacent suspensory branch (OR 4.56, 95% CI 2.18-9.53, P = 0.0001). Conclusions This study reveals that the grading scale used is important when providing prognostic advice on the significance of radiographic signs of sesamoiditis. Evidence of significant sesamoiditis implies a 5 times greater risk of developing clinical SLBI with the onset of training. Clinicians should be aware that sesamoiditis may be an indicator of future SLBI in yearlings which are clinically normal at the time of sale.