title: The sacroiliac joints: evaluation using nuclear scintigraphy. Part 2: Lame horses.
abstract: BACKGROUND
  Sacroiliac (SI) joint disease is difficult to diagnose definitively on clinical grounds.
  
  
  OBJECTIVE
  Lameness not attributable to SI joint pain may result in asymmetrical uptake of radiopharmaceutical in the tubera sacrale and SI joints; and that horses with clinical signs suggestive of sacroiliac joint disease would have differences in the ratios of radiopharmaceutical uptake between the fifth lumbar vertebra (L5) and either the tubera sacrale or SI joints compared with normal horses.
  
  
  OBJECTIVE
  To determine whether differences in radiopharmaceutical activity could identify individuals with presumed SI joint region pain.
  
  
  METHODS
  The scintigraphic appearance of the pelvic region of 234 horses (Group I) with lameness unrelated to the SI joints was compared with that for 40 normal horses (Group N) in full work and that for 41 horses with suspected SI joint disease (Group II). The effect of age, sex, lame limb and discipline were assessed in Group I. Motion-corrected scintigraphic images were assessed grossly, using profile analysis and by comparing ratios of uptake of mean count per pixel between L5 and each of the left (L) tuber sacrale (TS), right (R) TS, LSI and RSI joints. Left-right symmetry was compared.
  
  
  RESULTS
  Lame horses (Group I) had greater asymmetry of radiopharmaceutical uptake in the tubera sacrale compared with normal horses. Horses with right hindlimb lameness had a larger RSI/LSI ratio compared to normal horses. In Group I L5/LTS, L5/RTS and L5/RSI increased with age, and there was a trend for L5/LSI to increase with age. In horses with presumed sacroiliac joint disease (Group II), L5/LTS, L5/RTS and L5/RSI were all greater compared with normal horses. Detection of marked left-right asymmetry by quantitative analysis or profile analysis was helpful in discriminating between those horses with clinical signs compatible with SI joint disease and either normal horses or those lame due to another cause.
  
  
  CONCLUSIONS
  Scintigraphic evaluation of the SI region is useful to identify SI joint disease in combination with other clinical signs supportive of the diagnosis. However, diagnosis should not be based on this alone because of some degree of overlap in the range of radiopharmaceutical uptake between horses with SI joint disease and both normal horses and those with other causes of lameness.
authors.affiliation: Centre for Equine Studies, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK.
authors.forename: S
authors.initials: S
authors.lastname: Dyson
authors.forename: R
authors.initials: R
authors.lastname: Murray
authors.forename: M
authors.initials: M
authors.lastname: Branch
authors.forename: E
authors.initials: E
authors.lastname: Harding
mesh_terms: D000367:Age Factors; D000818:Animals; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D005260:Female; D006614:Hindlimb / Q000503:physiopathology; D006734:Horse Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging*; D006736:Horses; D007091:Image Processing, Computer-Assisted; D007794:Lameness, Animal / Q000175:diagnosis / Q000000981:diagnostic imaging*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008297:Male; D011877:Radionuclide Imaging; D012446:Sacroiliac Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D012447:Sacrum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D013669:Technetium Tc 99m Medronate
chemical_list: D013669:Technetium Tc 99m Medronate