Canine Femoral Trochlear Dysplasia: A Retrospective Study Assessing the Dejour Signs.

CT lateral reconstructions reliably detect Dejour trochlear dysplasia signs in dogs, supporting preoperative surgical planning for patellar luxation.

This retrospective study evaluated whether Dejour's lateral radiographic signs of femoral trochlear dysplasia—crossing sign, supratrochlear spur, and double contour—are identifiable in dogs with and without patellar luxation (PL), and whether CT lateral reconstructions can serve as an alternative to conventional radiography. Forty femoral trochleae were assessed: 15 controls (no PL) and 25 PL-affected stifles. A blinded observer evaluated mediolateral radiographs and CT-based lateral reconstructions randomized for reading order. Dejour signs were essentially absent in control dogs (one incidental CT finding), confirming high specificity. In PL-affected stifles, one or more Dejour signs were present in 68% on radiography and 72% on CT, with individual sign prevalence (crossing 48%, supratrochlear spur 40-44%, double contour 28%) remaining consistent between modalities. Agreement between radiography and CT was substantial to near-perfect (κ 0.89–1.00; observed agreement 95–100%), supporting CT lateral reconstructions as a reliable substitute for radiography in detecting trochlear dysplasia. A novel 'dome sign'—a single projection line indicating a convex trochlea—was identified in 24% of PL trochleae on both modalities, predominantly in grade-4 PL cases. This ancillary finding may indicate more severe trochlear abnormality requiring more aggressive surgical intervention such as trochlear replacement. The study supports integrating Dejour sign assessment and the proposed dome sign into preoperative planning for canine PL, potentially guiding surgical decision-making including the choice of trochleoplasty technique.

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