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

Area of Science:

• Veterinary Radiology
• Canine Orthopedics
• Comparative Anatomy

Background:

• Femoral trochlear dysplasia is a common cause of patellar luxation (PL) in dogs.
• Dejour's radiographic signs are used to diagnose femoral trochlear dysplasia in humans.
• Their applicability and reliability in canine stifle joints, particularly in conjunction with computed tomography (CT), require investigation.

Purpose of the Study:

• To determine if Dejour's lateral radiographic signs of femoral trochlear dysplasia are identifiable in healthy dogs and dogs with patellar luxation (PL).
• To evaluate if CT lateral reconstructions can serve as a substitute for radiography in assessing these signs.
• To explore the diagnostic utility of these signs and the 'dome' sign in canine PL.

Main Methods:

• Forty femoral trochleae were analyzed: 15 controls (no PL) and 25 with PL.
• Mediolateral stifle radiographs and CT-based lateral reconstructions were performed.
• A blinded observer assessed both modalities for Dejour signs (crossing, supratrochlear spur, double contour).
• Agreement between radiography and CT was statistically evaluated using Cohen's kappa and McNemar's test.

Main Results:

• Dejour signs were rare in controls but present in 68% of PL stifles on radiographs and 72% on CT.
• Radiographic and CT findings showed substantial agreement in PL stifles (observed agreement 95-100%, kappa 0.89-1.00).
• A 'dome' sign (convex trochlea) was observed in 24% of PL trochleae on both modalities, often in grade-4 PL.

Conclusions:

• Dejour signs are valuable indicators of femoral trochlear dysplasia in dogs with PL and are infrequently found in healthy dogs.
• CT lateral reconstructions are a reliable alternative to radiography for identifying these signs in canine patellar luxation.
• Recognizing Dejour and 'dome' signs can aid in preoperative planning and surgical decision-making for canine PL.