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

The aim of this study was to assess whether Dejour's lateral radiographic signs of femoral trochlear dysplasia are identifiable in healthy and patellar luxation (PL)-affected dogs; and whether computed tomography (CT) lateral reconstructions can substitute for radiography.

Forty femoral trochleae were divided into controls without PL (n = 15) and dogs with PL (n = 25). Mediolateral stifle radiographs and CT-based lateral reconstructions were randomized and read by a blinded observer for Dejour signs (crossing, supratrochlear spur, double contour). Agreement between modalities was evaluated with Cohen's kappa and McNemar's test (p < 0.05).

Dejour signs were absent from controls on both modalities except for one CT trochlea. In controls, method agreement for femoral trochlear dysplasia signs (one or more signs) was high (observed agreement 93%). In PL stifles, one or more Dejour signs were present in 68% on radiographs and 72% on CT. On radiographs: crossing 48%, supratrochlear spur 40%, double contour 28%; and on CT: 48%, 44%, 28%, respectively. Sign combinations occurred in 36%. Agreement between radiography and CT in PL stifles was substantial (observed agreement 95-100%; κ 0.89-1.00). An ancillary finding - a single projection line consistent with a convex trochlea ('dome' sign) - was observed in 24% of PL trochleae both with radiography and CT, mostly grade-4 PL.

Dejour femoral trochlear dysplasia signs are identifiable in dogs with PL and rare in normal dogs. Computed tomography lateral reconstructions reliably depict these features and may substitute for radiography. Recognition of Dejour sign and the proposed dome sign may aid preoperative planning and surgical decision-making in canine PL.