title: Ultrasonographic assessment of the superficial digital flexor tendons of National Hunt racehorses in training over two racing seasons.
abstract: BACKGROUND
  It is important to ascertain the prevalence of superficial digital flexor tendon (SDFT) injuries and to improve methods of predicting injury in National Hunt (NH) racehorses.
  
  
  OBJECTIVE
  To establish: 1) the prevalence of SDFT tendinopathy in NH horses; 2) whether routine ultrasonography can be used to predict SDFT injuries; 3) whether previous tendinopathy predisposes to reinjury; 4) a normal range for the SDFT cross-sectional area (CSA); and 5) the effects of gender, age, background (ex-flat or ex-store), limb, training and rest periods on SDFT CSA.
  
  
  METHODS
  Routine ultrasound assessment of the palmar metacarpal soft tissues of 263 NH racehorses was performed on up to 6 occasions over 2 NH racing seasons.
  
  
  RESULTS
  The prevalence of SDFT pathology detected using ultrasonography was 24% (n = 148), with a nonsignificant variation between yards of 10-40%. No changes in SDFT CSA or ultrasonographic appearance were detected prior to injury. Older horses had a significantly higher prevalence of SDFT pathology compared to younger horses, and horses with tendinopathy were more likely to suffer an acute injury compared to horses with no evidence of pathology. A reference range for normal CSA measurements was established as 77-139 mm2 at level 4, from 142 horses with no ultrasonographic evidence of SDFT pathology. The CSA of normal horses did not vary significantly with age, limb or over 2 racing seasons, but did with sex and background.
  
  
  CONCLUSIONS
  The study confirms that SDFT tendinopathy is common in NH horses, with substantial variation between training yards. Ultrasonography at 3 month intervals did not seem to predict acute SDFT injuries.
  
  
  CONCLUSIONS
  Variation in the prevalence of tendinopathy between yards suggests that training methods may influence injury rate. It was not possible to predict injury using routine ultrasonography and therefore other methods must be identified. A normal reference range for SDFT CSA is provided.
authors.affiliation: Department of Veterinary Clinical Sciences, Royal Veterinary College, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire AL9 7TA, UK.
authors.forename: C S
authors.initials: CS
authors.lastname: Avella
authors.forename: E R
authors.initials: ER
authors.lastname: Ely
authors.forename: K L P
authors.initials: KL
authors.lastname: Verheyen
authors.forename: J S
authors.initials: JS
authors.lastname: Price
authors.forename: J L N
authors.initials: JL
authors.lastname: Wood
authors.forename: R K W
authors.initials: RK
authors.lastname: Smith
mesh_terms: D000818:Animals; D005260:Female; D005552:Forelimb / Q000000981:diagnostic imaging / Q000473:pathology; D006734:Horse Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D006736:Horses; D008297:Male; D010805:Physical Conditioning, Animal; D013708:Tendon Injuries / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary*; D013997:Time Factors; D014463:Ultrasonography