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Objective

To determine the value of 2 diagnostic methods: (1) the reduction angle (RA) using the Ortolani maneuver and (2) the dorsal acetabular slope (DAS) from the dorsal acetabular rim (DAR) radiographic projection, to predict osteoarthritis (OA) in dogs with hip dysplasia.

Study Design

Prospective study.

Sample Population

Dogs (n = 73).

Methods

Hip-extended ventrodorsal (VD) radiographic projections, RA, and DAS were evaluated when dogs were 6, 12, and 24 months of age. VD projections were qualitatively scored for OA. RA was determined using the Ortolani maneuver in dorsal recumbency and DAS using the DAR projection. Distraction index (DI) measurements from the compression–distraction radiographic projections (PennHIP method) were also performed at 6 months of age. Statistical analyses were used to establish the range of values of normal and abnormal RA and DAS, to document the temporal variation in RA and DAS, to compare the ability of the different methods to predict coxofemoral OA, to determine the influence of pure passive laxity and of the DAS on the occurrence of an Ortolani sign and on the magnitude of the RA, to establish the relationship between the DAS and subsequent development of passive laxity and coxofemoral OA, and to evaluate the influence of the DAS and RA on the occurrence of coxofemoral OA with severe, moderate, and minimal coxofemoral passive joint laxity, respectively.

Results

VD, RA, DAS, and DI methods of coxofemoral joint evaluation correlated significantly with the status of the coxofemoral joints at 2 years of age. The risk of occurrence of coxofemoral OA increased, as the RA, DAS, or DI increased. There was a significant positive linear relationship between RA and DI (P = .015, r2 = 0.32), RA and DAS (P = .0078, r2 = 0.38), and DAS and DI (P = .015, r2 = 0.33). A negative Ortolani sign was at all times significantly predictive of absence of coxofemoral OA at 2 years of age. DAS best predicted coxofemoral OA for DI ≥ 0.7, whereas RA best predicted coxofemoral OA for 0.3 < DI < 0.7; however, RA proved to be the best overall predictor of coxofemoral OA.

Conclusion

RA measured at 6 months of age in dorsal recumbency was the best predictor of coxofemoral OA at 2 years of age.