Objectives The main purpose of this article is to evaluate the correlation between the distraction index (DI) and Norberg angle values in distracted hips (distraction Norberg angle, DNA) at 4 months of age and the official hip score based on the Fédération Cynologique Internationale (FCI) grid at 12 months of age.
Methods For dogs (n = 215) from two guide dog training organizations, the DI and DNA were measured by a single expert on distraction radiographs performed at 4 months of age. The FCI score was determined by the same expert at 12 months of age on a standard hip-extended view.
Statistical analysis included receiver operating characteristic curve analysis and concordance correlation coefficient calculation.
Results The mean DI was 0.48, the mean DNA was 86.5° and 59.5% of hips had an A FCI score. The concordance correlation coefficient of DI and DNA was 0.78. The DI threshold for D- and E-scored hips that was associated with the least misclassification was 0.58 (sensitivity [Se] = 0.6, specificity [Sp] = 0.82). The DNA threshold that was associated with the least misclassification was 85° (Se = 0.83, Sp = 0.68).
Clinical Significance DNA has a fair correlation with DI at 4 months and reflects hip passive laxity. D and E FCI scores at 12 months cannot be reliably predicted from the 4 months value of DI or DNA but 96% of hips with DI < 0.58 at 4 months had an A, B or C FCI score at 12 months of age. Similarly, 98% of hips with DNA > 85° at 4 months had an A, B or C FCI score at 12 months of age.
|Publication Title||Veterinary and Comparative Orthopaedics and Traumatology|
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