title: Quantitative analysis of scintigraphic findings in tibial stress fractures in Thoroughbred racehorses.
abstract: OBJECTIVE
  To develop a quantitative method of interpreting tibial scintigrams of Thoroughbred racehorses with tibial stress fractures that may facilitate diagnosis of fractures and to provide prognostic information regarding future performance of affected horses.
  
  
  METHODS
  35 Thoroughbred racehorses.
  
  
  METHODS
  Static bone-phase scintigrams of tibial stress fractures were quantitatively analyzed by use of ratios of the mean radionuclide counts per pixel in a region of interest (ROI) drawn around the area of increased uptake of radiopharmaceutical to mean counts per pixel in a second ROI drawn around an apparently normal area of the tibial diaphysis. In horses with unilateral fractures, ratios for the contralateral tibia were determined by use of 2 ROIs drawn at the same positions as the ROIs in the fractured tibia. Ratios were compared between fractured versus apparently normal tibias, between horses that returned to racing versus those that did not, and among horses with various grades of lameness. The association between ratios for fractured tibias and intervals between diagnosis and return to racing was also assessed.
  
  
  RESULTS
  Mean ratio of ROIs in apparently normal tibias was 1.35 (95% confidence interval [CI], 1.21 to 1.50); that in tibias with stress fractures was 3.55 (95% CI, 2.50 to 4.60). These ratios were significantly different. None of the associations between ratios for fractured tibias and grades of lameness or performance outcomes were significant.
  
  
  CONCLUSIONS
  Tibial stress fracture scintigrams can be quantitatively analyzed. A prospective study with a controlled rehabilitation period is necessary to evaluate the possible applications of this method.
authors.affiliation: Department of Clinical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104-6044, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Valdés-Martínez
authors.forename: Gabriela
authors.initials: G
authors.lastname: Seiler
authors.forename: Wilfried
authors.initials: W
authors.lastname: Mai
authors.forename: David M
authors.initials: DM
authors.lastname: Bolt
authors.forename: Margaret
authors.initials: M
authors.lastname: Mudge
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Dukti
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Hubert
mesh_terms: D000818:Animals; D005260:Female; D015775:Fractures, Stress / Q000000981:diagnostic imaging* / Q000662:veterinary*; D006736:Horses / Q000293:injuries*; D008297:Male; D011877:Radionuclide Imaging / Q000379:methods / Q000662:veterinary*; D019275:Radiopharmaceuticals; D018709:Statistics, Nonparametric; D013669:Technetium Tc 99m Medronate / Q000031:analogs & derivatives; D013978:Tibial Fractures / Q000000981:diagnostic imaging* / Q000662:veterinary*
chemical_list: D019275:Radiopharmaceuticals; C024226:technetium Tc 99m hydroxymethylene diphosphonate; D013669:Technetium Tc 99m Medronate