title: The S-measurement in the diagnosis of canine hip dysplasia.
abstract: OBJECTIVE
  To propose a direct measure of subluxation of the femoral head (S) in the assessment of hip joint laxity and evaluate it for clinical use.
  
  
  METHODS
  Method comparison study.
  
  
  METHODS
  Dogs (n = 51).
  
  
  METHODS
  Dogs were sedated or anesthetized for a dorsolateral subluxation (DLS) examination. Two sets of radiographs were acquired, 1 each by a different technologist. A calibrated measuring bar was included on the image at the height of the hip to assess magnification. The DLS was calculated for each hip and different persons unaware of these details measured the "S"-value. One person measured the S-value 3 times over 3 days. Box plots were used to determine a cut-off for the empiric (8 mm) and corrected (4 mm) S-value.
  
  
  RESULTS
  Of 51 dogs, 33 were dysplastic based on a DLS score <55%. Magnification and body weight were strongly correlated (r = 0.4922, P = .0006). Both empiric and corrected S measurements showed good agreement with the DLS score (κ = 0.688 and κ = 0.681, respectively). The corrected S measurement produced more false negatives. Bland-Altman analysis showed interobserver and technician variance acceptable for clinical use (limits of agreement < ±3 mm). Intraobserver repeatability was acceptable for the right hip (95% of differences were ≤1.3 mm and 100% ≤ 1.9) but not for the left hip.
  
  
  CONCLUSIONS
  Using a cut-off value of 5 mm, the empirical S measurement can be used to exclude hip dysplasia in young dogs of various body proportions.
authors.affiliation: Department of Veterinary Clinical Sciences, Louisiana State University, Baton Rouge, LA 70810, USA. dogden@vetmed.lsu.edu
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Ogden
authors.forename: Peter V
authors.initials: PV
authors.lastname: Scrivani
authors.forename: Nathan
authors.initials: N
authors.lastname: Dykes
authors.forename: George
authors.initials: G
authors.lastname: Lust
authors.forename: Steven G
authors.initials: SG
authors.lastname: Friedenberg
authors.forename: Rory J
authors.initials: RJ
authors.lastname: Todhunter
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D004285:Dogs; D005260:Female; D006617:Hip Dislocation / Q000662:veterinary*; D006619:Hip Dysplasia, Canine / Q000000981:diagnostic imaging / Q000473:pathology*; D006621:Hip Joint / Q000473:pathology; D008297:Male; D011859:Radiography