title: Evaluation of experimentally induced injury to the superficial digital flexor tendon in horses by use of low-field magnetic resonance imaging and ultrasonography.
abstract: OBJECTIVE
  To evaluate tendon injuries in horses over a 16-week period by use of ultrasonography and low-field magnetic resonance imaging (MRI).
  
  
  METHODS
  Tendons of 8 young adult horses.
  
  
  METHODS
  The percentage of experimentally induced tendon injury was evaluated in cross section at the maximal area of injury by use of ultrasonography and MRI at 3, 4, 6, 8, and 16 weeks after collagenase injection. The MRI signal intensities and histologic characteristics of each tendon were determined at the same time points.
  
  
  RESULTS
  At 4 weeks after collagenase injection, the area of maximal injury assessed on cross section was similar between ultrasonography and MRI. In lesions of > 4 weeks' duration, ultrasonography underestimated the area of maximal cross-sectional injury by approximately 18%, compared with results for MRI. Signal intensity of lesions on T1-weighted images was the most hyperintense of all the sequences, lesions on short tau inversion recovery images were slightly less hyperintense, and T2-weighted images were the most hypointense. Signal intensity of tendon lesions was significantly higher than the signal intensity for the unaltered deep digital flexor tendon. Histologically, there was a decrease in proteoglycan content, an increase in collagen content, and minimal change in fiber alignment during the 16 weeks of the study.
  
  
  CONCLUSIONS
  Ultrasonography may underestimate the extent of tendon damage in tendons with long-term injury. Low-field MRI provided a more sensitive technique for evaluation of tendon injury and should be considered in horses with tendinitis of > 4 weeks' duration.
authors.affiliation: Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802, USA. dr_karlin@midatlanticequine.com
authors.forename: William M
authors.initials: WM
authors.lastname: Karlin
authors.forename: Allison A
authors.initials: AA
authors.lastname: Stewart
authors.forename: Sushmitha S
authors.initials: SS
authors.lastname: Durgam
authors.forename: James F
authors.initials: JF
authors.lastname: Naughton
authors.forename: Kristen J
authors.initials: KJ
authors.lastname: O'Dell-Anderson
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Stewart
mesh_terms: D000818:Animals; D017364:Collagenases / Q000009:adverse effects; D006736:Horses; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000662:veterinary*; D010341:Pathology, Veterinary / Q000295:instrumentation / Q000379:methods*; D013708:Tendon Injuries / Q000175:diagnosis / Q000662:veterinary*; D014463:Ultrasonography / Q000379:methods / Q000662:veterinary*
chemical_list: D017364:Collagenases