Computed tomographic measurements of the femoral trochlea in dogs with and without medial patellar luxation.

Abstract

OBJECTIVES: To determine cutoff values in small (SB) and medium/large (MLB) breed dogs with and without medial patellar luxation (MPL) for identifying abnormal femoral trochlea morphology. STUDY DESIGN: Original research. ANIMALS: A total of 80 computed tomographic (CT) scans from client-owned dogs METHODS: Four groups of 20 dogs were created: (1) control SB, (2) control MLB, (3) MPL-SB, and (4) MPL-MLB. Two authors measured the femoral trochlear groove angle (FTGA), femoral trochlear angle (FTA), and femoral trochlear ridge inclination angle (FTRIA) in two points with CT. ANOVA and ROC-analysis were tested to the control and MPL groups to assess sensitivity, specificity, and cutoff values. Statistical significance was set to p&#x2009;<&#x2009;.05. Intraclass correlation coefficients evaluated the inter-rater agreement. RESULTS: FTGA (&#xb1; SD) in control SB (128.8&#xb0;&#x2009;&#xb1;&#x2009;4.7&#xb0;) and control MLB (119.2&#xb0; &#xb1;&#x2009;5.6&#xb0;), was smaller (p&#x2009;<&#x2009;.0001) than in MPL-SB (139.4&#xb0;&#x2009;&#xb1;&#x2009;4.4&#xb0;) and MPL-MLB (133.7&#xb0; &#xb1;&#x2009;5.1&#xb0;). FTA and FTRIA were decreased (p&#xa0;=&#xa0;.12, p&#xa0;=&#xa0;.23) in MPL-SB (2.1&#xb0; &#xb1;&#x2009;6.8; -0.3&#xb0; &#xb1;&#x2009;3.3&#xb0;) and MPL-MLB (3.8&#xb0; &#xb1;&#x2009;5.6&#xb0;; 1.7&#xb0; &#xb1;&#x2009;4.5&#xb0;) compared to control SB (0.2&#xb0; &#xb1;4.1; -0.1&#xb0;&#x2009;&#xb1;&#x2009;2.6&#xb0;) and control MLB (5.3&#xb0;&#x2009;&#xb1;&#x2009;2.8&#xb0;; 3.1&#xb0; &#xb1;&#x2009;1.3&#xb0;). Cutoff values for FTGA, FTA, and FTRIA were&#x2009;>&#x2009;134&#xb0;, < -5.9&#xb0;, < -2 &#xb0; (SB), and&#x2009;>&#x2009;128.3&#xb0;, < -0.4&#xb0;, < -0.4&#xb0; (MLB). Sensitivity, specificity, and inter-rater agreement were superior for FTGA than FTA and FTRIA. CONCLUSIONS: Dogs without MPL had a deeper femoral trochlear groove than MPL dogs. SB had a shallower groove than MLB. The measurement of FTA and FTRIA was not reliable. CLINICAL RELEVANCE: A FTGA <134&#xb0; (SB) and&#x2009;<&#x2009;128&#xb0; (MLB) may be considered as a cutoff for trochleoplasty decision-making.