Within- and between-examiner repeatability of distraction indices of the hip joints in dogs

Objective - To evaluate in vivo repeatability of the distraction index method of evaluating hip joint laxity in dogs. Animals - 31 two-year-old Labrador Retrievers. Procedure - Each dog was anesthetized and radiographically evaluated for hip joint laxity 4 times: twice by an experienced examiner and twice by an examiner who had no previous knowledge of or training in the technique prior to the first day of testing. Distraction indices (DI) were determined from the radiographs and intraclass correlation coefficients were calculated to evaluate the repeatability of DI measurements between and within examiners. Results - Intraclass correlation coefficients were high (range, 0.85 to 0.94). Lower limits of the 95% confidence intervals for the intraclass correlation coefficients ranged from 0.75 to 0.89. Conclusions - Between- and within-examiner repeatabilities of DI measurements were high, suggesting that the technique is clinically reliable. Clinical Relevance - Distraction index is a reliable measure of hip joint laxity and a good predictor of the risk of development of degenerative joint disease associated with hip dysplasia in dogs. Establishment of high repeatability of DI measurements suggests that the stress-radiographic method may be used by multiple examiners with the expectation of comparable and consistent results.