Comparison of three distraction methods and conventional radiography for early diagnosis of canine hip dysplasia


S. Ohlerth's present address is the Section of Diagnostic Imaging and Radio-Oncology, Veterinary Faculty, University of Zürich, Winterthurerstrasse 260, 8057 Zürich, Switzerland


Two radiographic distraction techniques (one employing a wooden lath and, the other, a PennHip distractor), an ultrasonographic distraction method and conventional radiographic Fédération Cynologique Internationale (FCI) hip score were evaluated in eight-month-old Labrador retrievers to determine the most reliable method for predicting radiographic FCI hip score at the age of one year. With reference to the FCI hip score, sensitivity and specificity of the PennHip method were 100 per cent and 54 per cent; sensitivity and specificity of the lath technique were 85 per cent and 71 per cent; whereas they were 62 per cent and 67 per cent for the ultrasonographic method. For all distraction methods, the positive predictive value (PPV) was moderate and the negative predictive value (NPV) was high. Sensitivity, specificity, PPV and NPV were 100 per cent for the FCI hip score. It is concluded that, at the age of eight months, FCI hip score is the most reliable method for predicting FCI hip score at the age of one year in the colony of dogs investigated. Both the PennHip and lath method were also clinically reliable techniques in predicting true negatives. The ultrasonographic distraction method was moderately reliable.