Ever heard of Déjour classification for stifle?

Computed Tomography Evaluation of Morphological Types of Femoral Trochlear Dysplasia in Small-Breed Dogs-A Retrospective Study

Radka S Garnoeva 1

Background
Trochlear dysplasia is a three-dimensional deformity that compromises the femoral trochlear groove, increasing the risk of medial patellar luxation in small-breed dogs. Although the condition's association with patellar instability is established, its prevalence in the general population and specific dysplasia types remain underexplored. This study applied Déjour's classification (types A, B, C, D) for trochlear dysplasia in small-breed dogs using computed tomography (CT) to evaluate its prevalence and relationship with breed, sex, and patellar luxation grade.

Methods
Study Design: Retrospective study of 174 stifles from 128 dogs (Miniature Pinschers, Yorkshire Terriers, Pomeranians, and Chihuahuas) aged 1.5–4 years.

Sample Grouping:
-Affected Group: 106 stifles with medial patellar luxation (96 grade II, 10 grade III).
-Control Group: 68 orthopedically healthy stifles.

CT Protocol: High-resolution axial and 3D reconstructed CT scans were used to measure sulcus angle, trochlear depth, and inclination angles.

Classification: Trochlear dysplasia types were identified using Déjour's four-type system. Statistical analyses compared findings across breeds, sex, and luxation grades.

Results
Prevalence:
-Trochlear dysplasia was identified in 140 stifles (80.5%), including all luxated stifles and 50% of healthy stifles.
-Most common type: Type A (59.3%), followed by type C (34.3%) and type D (5.7%). Type B (0.7%) was rare.

Breed Variability:
-Miniature Pinschers had the highest dysplasia prevalence (35%), with type A being most frequent.
-In Pomeranians, type C predominated (29% prevalence).

Sex Differences:
Dysplasia was significantly more common in females, particularly type C dysplasia (twice as frequent in females compared to males).

Patellar Luxation Correlation:
-Grade II luxation was associated primarily with types A (53%) and C (42.7%), while grade III luxation exclusively involved types C (50%) and D (50%).

Morphometric Findings:
-Sulcus angles were larger, and trochlear depths were significantly reduced in dysplastic joints compared to normal stifles (p < 0.001).
-Type D dysplasia showed extreme deformities, with a dome-shaped groove and no measurable trochlear depth.

Limitations
The study excluded stifles with traumatic luxation and grade IV luxation. It was limited to four small dog breeds, which may not represent other breeds. Interobserver agreement was not assessed for the classification system.

Conclusions
The Déjour classification system is effective for characterizing trochlear dysplasia in small-breed dogs. The high prevalence of trochlear dysplasia, even in clinically healthy joints, underscores the need for early imaging evaluations in predisposed breeds, especially female breeders. The findings highlight the role of trochlear dysplasia as a primary contributor to medial patellar luxation and suggest the importance of integrating bony stabilizer assessments into orthopedic decision-making.

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